misc_cursors.test.js

'use strict';
const { assert: test, filterForCommands, setupDatabase } = require('../shared');
const { runLater, sleep } = require('../../tools/utils');
const fs = require('fs');
const os = require('os');
const path = require('path');
const { expect } = require('chai');
const BSON = require('bson');
const sinon = require('sinon');
const { Writable } = require('stream');
const { setTimeout } = require('timers');
const { ReadPreference } = require('../../mongodb');
const { ServerType } = require('../../mongodb');
const { formatSort } = require('../../mongodb');
const { getSymbolFrom } = require('../../tools/utils');

describe('Cursor', function () {
  before(function () {
    return setupDatabase(this.configuration, [
      'cursorkilltest1',
      'cursor_session_tests',
      'cursor_session_tests2'
    ]);
  });

  let client;
  beforeEach(async function () {
    client = this.configuration.newClient({ maxPoolSize: 1, monitorCommands: true });
  });
  afterEach(async function () {
    await client.close();
  });

  it('should not throw an error when toArray and forEach are called after cursor is closed', async function () {
    const db = client.db();

    const collection = await db.collection('test_to_a');
    await collection.insertMany([{ a: 1 }]);
    const cursor = collection.find({});

    const firstToArray = await cursor.toArray().catch(error => error);
    expect(firstToArray).to.be.an('array');

    expect(cursor.closed).to.be.true;

    const secondToArray = await cursor.toArray().catch(error => error);
    expect(secondToArray).to.be.an('array');
    expect(secondToArray).to.have.lengthOf(0);

    const forEachResult = await cursor
      .forEach(() => {
        expect.fail('should not run forEach on an empty/closed cursor');
      })
      .catch(error => error);
    expect(forEachResult).to.be.undefined;
  });

  it('cursor should close after first next operation', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('close_on_next', (err, collection) => {
          expect(err).to.not.exist;

          collection.insert(
            [{ a: 1 }, { a: 1 }, { a: 1 }],
            configuration.writeConcernMax(),
            err => {
              expect(err).to.not.exist;

              var cursor = collection.find({});
              this.defer(() => cursor.close());

              cursor.batchSize(2);
              cursor.next(err => {
                expect(err).to.not.exist;
                done();
              });
            }
          );
        });
      });
    }
  });

  it('cursor should trigger getMore', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('trigger_get_more', (err, collection) => {
          expect(err).to.not.exist;

          collection.insert(
            [{ a: 1 }, { a: 1 }, { a: 1 }],
            configuration.writeConcernMax(),
            err => {
              expect(err).to.not.exist;
              const cursor = collection.find({}).batchSize(2);
              this.defer(() => cursor.close());
              cursor.toArray(err => {
                expect(err).to.not.exist;
                done();
              });
            }
          );
        });
      });
    }
  });

  it('shouldCorrectlyExecuteCursorExplain', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_explain', (err, collection) => {
          expect(err).to.not.exist;

          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            collection.find({ a: 1 }).explain((err, explanation) => {
              expect(err).to.not.exist;
              expect(explanation).to.exist;
              done();
            });
          });
        });
      });
    }
  });

  it('shouldCorrectlyExecuteCursorCount', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_count', (err, collection) => {
          expect(err).to.not.exist;

          collection.find().count(err => {
            expect(err).to.not.exist;

            function insert(callback) {
              var total = 10;

              for (var i = 0; i < 10; i++) {
                collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                  expect(e).to.not.exist;
                  total = total - 1;
                  if (total === 0) callback();
                });
              }
            }

            function finished() {
              collection.find().count((err, count) => {
                expect(err).to.not.exist;
                test.equal(10, count);
                test.ok(count.constructor === Number);

                collection.find({}, { limit: 5 }).count((err, count) => {
                  expect(err).to.not.exist;
                  test.equal(5, count);

                  collection.find({}, { skip: 5 }).count((err, count) => {
                    expect(err).to.not.exist;
                    test.equal(5, count);

                    db.collection('acollectionthatdoesn').count((err, count) => {
                      expect(err).to.not.exist;
                      test.equal(0, count);

                      var cursor = collection.find();
                      cursor.count((err, count) => {
                        expect(err).to.not.exist;
                        test.equal(10, count);

                        cursor.forEach(
                          () => {},
                          err => {
                            expect(err).to.not.exist;
                            cursor.count((err, count2) => {
                              expect(err).to.not.exist;
                              expect(count2).to.equal(10);
                              expect(count2).to.equal(count);
                              done();
                            });
                          }
                        );
                      });
                    });
                  });
                });
              });
            }

            insert(function () {
              finished();
            });
          });
        });
      });
    }
  });

  it('should correctly execute cursor count with secondary readPreference', {
    metadata: { requires: { topology: 'replicaset' } },
    async test() {
      const bag = [];
      client.on('commandStarted', filterForCommands(['count'], bag));

      const cursor = client
        .db()
        .collection('countTEST')
        .find({ qty: { $gt: 4 } });
      await cursor.count({ readPreference: ReadPreference.SECONDARY });

      const selectedServerAddress = bag[0].address
        .replace('127.0.0.1', 'localhost')
        .replace('[::1]', 'localhost');
      const selectedServer = client.topology.description.servers.get(selectedServerAddress);
      expect(selectedServer).property('type').to.equal(ServerType.RSSecondary);
    }
  });

  it('shouldCorrectlyExecuteCursorCountWithDottedCollectionName', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_count.ext', (err, collection) => {
          expect(err).to.not.exist;

          collection.find().count(err => {
            expect(err).to.not.exist;

            function insert(callback) {
              var total = 10;

              for (var i = 0; i < 10; i++) {
                collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                  expect(e).to.not.exist;
                  total = total - 1;
                  if (total === 0) callback();
                });
              }
            }

            function finished() {
              collection.find().count((err, count) => {
                expect(err).to.not.exist;
                test.equal(10, count);
                test.ok(count.constructor === Number);

                collection.find({}, { limit: 5 }).count((err, count) => {
                  expect(err).to.not.exist;
                  test.equal(5, count);

                  collection.find({}, { skip: 5 }).count((err, count) => {
                    expect(err).to.not.exist;
                    test.equal(5, count);

                    db.collection('acollectionthatdoesn').count((err, count) => {
                      expect(err).to.not.exist;
                      test.equal(0, count);

                      var cursor = collection.find();
                      cursor.count((err, count) => {
                        expect(err).to.not.exist;
                        test.equal(10, count);

                        cursor.forEach(
                          () => {},
                          err => {
                            expect(err).to.not.exist;
                            cursor.count((err, count2) => {
                              expect(err).to.not.exist;
                              expect(count2).to.equal(10);
                              expect(count2).to.equal(count);
                              done();
                            });
                          }
                        );
                      });
                    });
                  });
                });
              });
            }

            insert(function () {
              finished();
            });
          });
        });
      });
    }
  });

  it('shouldThrowErrorOnEachWhenMissingCallback', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_each', (err, collection) => {
          expect(err).to.not.exist;
          function insert(callback) {
            var total = 10;

            for (var i = 0; i < 10; i++) {
              collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                expect(e).to.not.exist;
                total = total - 1;
                if (total === 0) callback();
              });
            }
          }

          function finished() {
            const cursor = collection.find();

            test.throws(function () {
              cursor.forEach();
            });

            done();
          }

          insert(function () {
            finished();
          });
        });
      });
    }
  });

  it('shouldCorrectlyHandleLimitOnCursor', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_cursor_limit', (err, collection) => {
          function insert(callback) {
            var total = 10;

            for (var i = 0; i < 10; i++) {
              collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                expect(e).to.not.exist;
                total = total - 1;
                if (total === 0) callback();
              });
            }
          }

          function finished() {
            collection
              .find()
              .limit(5)
              .toArray((err, items) => {
                test.equal(5, items.length);

                // Let's close the db
                expect(err).to.not.exist;
                done();
              });
          }

          insert(function () {
            finished();
          });
        });
      });
    }
  });

  it('shouldCorrectlyHandleNegativeOneLimitOnCursor', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_cursor_negative_one_limit', (err, collection) => {
          expect(err).to.not.exist;
          function insert(callback) {
            var total = 10;

            for (var i = 0; i < 10; i++) {
              collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                expect(e).to.not.exist;
                total = total - 1;
                if (total === 0) callback();
              });
            }
          }

          function finished() {
            collection
              .find()
              .limit(-1)
              .toArray((err, items) => {
                expect(err).to.not.exist;
                test.equal(1, items.length);

                // Let's close the db
                done();
              });
          }

          insert(function () {
            finished();
          });
        });
      });
    }
  });

  it('shouldCorrectlyHandleAnyNegativeLimitOnCursor', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_cursor_any_negative_limit', (err, collection) => {
          expect(err).to.not.exist;
          function insert(callback) {
            var total = 10;

            for (var i = 0; i < 10; i++) {
              collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                expect(e).to.not.exist;
                total = total - 1;
                if (total === 0) callback();
              });
            }
          }

          function finished() {
            collection
              .find()
              .limit(-5)
              .toArray((err, items) => {
                expect(err).to.not.exist;
                test.equal(5, items.length);

                // Let's close the db
                done();
              });
          }

          insert(function () {
            finished();
          });
        });
      });
    }
  });

  it('shouldCorrectlyReturnErrorsOnIllegalLimitValuesNotAnInt', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_limit_exceptions_2', (err, collection) => {
          expect(err).to.not.exist;

          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;
            const cursor = collection.find();
            this.defer(() => cursor.close());

            try {
              cursor.limit('not-an-integer');
            } catch (err) {
              test.equal('Operation "limit" requires an integer', err.message);
            }

            done();
          });
        });
      });
    }
  });

  it('shouldCorrectlyReturnErrorsOnIllegalLimitValuesIsClosedWithinNext', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_limit_exceptions', (err, collection) => {
          expect(err).to.not.exist;

          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            const cursor = collection.find();
            this.defer(() => cursor.close());

            cursor.next(err => {
              expect(err).to.not.exist;
              expect(() => {
                cursor.limit(1);
              }).to.throw(/Cursor is already initialized/);

              done();
            });
          });
        });
      });
    }
  });

  // NOTE: who cares what you set when the cursor is closed?
  it.skip('shouldCorrectlyReturnErrorsOnIllegalLimitValuesIsClosedWithinClose', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_limit_exceptions_1', (err, collection) => {
          expect(err).to.not.exist;

          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            const cursor = collection.find();
            cursor.close(err => {
              expect(err).to.not.exist;
              expect(() => {
                cursor.limit(1);
              }).to.throw(/not extensible/);

              done();
            });
          });
        });
      });
    }
  });

  it('shouldCorrectlySkipRecordsOnCursor', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_skip', (err, collection) => {
          expect(err).to.not.exist;

          const insert = callback => {
            var total = 10;
            for (var i = 0; i < 10; i++) {
              collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                expect(e).to.not.exist;

                total = total - 1;
                if (total === 0) callback();
              });
            }
          };

          insert(() => {
            const cursor = collection.find();
            this.defer(() => cursor.close());

            cursor.count((err, count) => {
              expect(err).to.not.exist;
              test.equal(10, count);
            });

            const cursor2 = collection.find();
            this.defer(() => cursor2.close());

            cursor2.toArray((err, items) => {
              expect(err).to.not.exist;
              test.equal(10, items.length);

              collection
                .find()
                .skip(2)
                .toArray((err, items2) => {
                  expect(err).to.not.exist;
                  test.equal(8, items2.length);

                  // Check that we have the same elements
                  var numberEqual = 0;
                  var sliced = items.slice(2, 10);

                  for (var i = 0; i < sliced.length; i++) {
                    if (sliced[i].x === items2[i].x) numberEqual = numberEqual + 1;
                  }

                  test.equal(8, numberEqual);
                  done();
                });
            });
          });
        });
      });
    }
  });

  it('shouldCorrectlyReturnErrorsOnIllegalSkipValues', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_skip_exceptions', (err, collection) => {
          expect(err).to.not.exist;
          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            try {
              collection.find().skip('not-an-integer');
            } catch (err) {
              test.equal('Operation "skip" requires an integer', err.message);
            }

            const cursor = collection.find();
            cursor.next(err => {
              expect(err).to.not.exist;

              // NOTE: who cares what you set when closed, if not initialized
              // expect(() => {
              //   cursor.skip(1);
              // }).to.throw(/not extensible/);

              const cursor2 = collection.find();
              cursor2.close(err => {
                expect(err).to.not.exist;

                // NOTE: who cares what you set when closed, if not initialized
                // expect(() => {
                //   cursor2.skip(1);
                // }).to.throw(/not extensible/);

                done();
              });
            });
          });
        });
      });
    }
  });

  it('shouldReturnErrorsOnIllegalBatchSizes', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_batchSize_exceptions', (err, collection) => {
          expect(err).to.not.exist;
          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            let cursor = collection.find();
            try {
              cursor.batchSize('not-an-integer');
              test.ok(false);
            } catch (err) {
              test.equal('Operation "batchSize" requires an integer', err.message);
            }

            cursor = collection.find();
            cursor.next(err => {
              expect(err).to.not.exist;

              cursor.next(err => {
                expect(err).to.not.exist;

                // NOTE: who cares what you set when closed, if not initialized
                // expect(() => {
                //   cursor.batchSize(1);
                // }).to.throw(/not extensible/);

                const cursor2 = collection.find();
                cursor2.close(err => {
                  expect(err).to.not.exist;

                  // NOTE: who cares what you set when closed, if not initialized
                  // expect(() => {
                  //   cursor2.batchSize(1);
                  // }).to.throw(/not extensible/);

                  done();
                });
              });
            });
          });
        });
      });
    }
  });

  it('shouldCorrectlyHandleBatchSize', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_multiple_batch_size', (err, collection) => {
          expect(err).to.not.exist;

          //test with the last batch that is a multiple of batchSize
          var records = 4;
          var batchSize = 2;
          var docs = [];
          for (var i = 0; i < records; i++) {
            docs.push({ a: i });
          }

          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            const cursor = collection.find({}, { batchSize: batchSize });

            //1st
            cursor.next((err, items) => {
              expect(err).to.not.exist;
              test.equal(1, cursor.bufferedCount());
              test.ok(items != null);

              //2nd
              cursor.next((err, items) => {
                expect(err).to.not.exist;
                test.equal(0, cursor.bufferedCount());
                test.ok(items != null);

                //3rd
                cursor.next((err, items) => {
                  expect(err).to.not.exist;
                  test.equal(1, cursor.bufferedCount());
                  test.ok(items != null);

                  //4th
                  cursor.next((err, items) => {
                    expect(err).to.not.exist;
                    test.equal(0, cursor.bufferedCount());
                    test.ok(items != null);

                    //No more
                    cursor.next((err, items) => {
                      expect(err).to.not.exist;
                      test.ok(items == null);
                      test.ok(cursor.closed);
                      done();
                    });
                  });
                });
              });
            });
          });
        });
      });
    }
  });

  it('shouldHandleWhenLimitBiggerThanBatchSize', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_limit_greater_than_batch_size', (err, collection) => {
          expect(err).to.not.exist;

          var limit = 4;
          var records = 10;
          var batchSize = 3;
          var docs = [];
          for (var i = 0; i < records; i++) {
            docs.push({ a: i });
          }

          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            var cursor = collection.find({}, { batchSize: batchSize, limit: limit });
            //1st
            cursor.next(err => {
              expect(err).to.not.exist;
              test.equal(2, cursor.bufferedCount());

              //2nd
              cursor.next(err => {
                expect(err).to.not.exist;
                test.equal(1, cursor.bufferedCount());

                //3rd
                cursor.next(err => {
                  expect(err).to.not.exist;
                  test.equal(0, cursor.bufferedCount());

                  //4th
                  cursor.next(err => {
                    expect(err).to.not.exist;

                    //No more
                    cursor.next((err, items) => {
                      expect(err).to.not.exist;
                      test.ok(items == null);
                      test.ok(cursor.closed);
                      done();
                    });
                  });
                });
              });
            });
          });
        });
      });
    }
  });

  it('shouldHandleLimitLessThanBatchSize', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_limit_less_than_batch_size', (err, collection) => {
          expect(err).to.not.exist;

          var limit = 2;
          var records = 10;
          var batchSize = 4;
          var docs = [];
          for (var i = 0; i < records; i++) {
            docs.push({ a: i });
          }

          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            var cursor = collection.find({}, { batchSize: batchSize, limit: limit });
            //1st
            cursor.next(err => {
              expect(err).to.not.exist;
              test.equal(1, cursor.bufferedCount());

              //2nd
              cursor.next(err => {
                expect(err).to.not.exist;
                test.equal(0, cursor.bufferedCount());

                //No more
                cursor.next((err, items) => {
                  expect(err).to.not.exist;
                  test.ok(items == null);
                  test.ok(cursor.closed);
                  done();
                });
              });
            });
          });
        });
      });
    }
  });

  it('shouldHandleSkipLimitChaining', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var collection = db.collection('shouldHandleSkipLimitChaining');

        function insert(callback) {
          var total = 10;

          for (var i = 0; i < 10; i++) {
            collection.insert({ x: i }, configuration.writeConcernMax(), e => {
              expect(e).to.not.exist;
              total = total - 1;
              if (total === 0) callback();
            });
          }
        }

        function finished() {
          collection.find().toArray((err, items) => {
            expect(err).to.not.exist;
            test.equal(10, items.length);

            collection
              .find()
              .limit(5)
              .skip(3)
              .toArray(function (err, items2) {
                expect(err).to.not.exist;
                test.equal(5, items2.length);

                // Check that we have the same elements
                var numberEqual = 0;
                var sliced = items.slice(3, 8);

                for (var i = 0; i < sliced.length; i++) {
                  if (sliced[i].x === items2[i].x) numberEqual = numberEqual + 1;
                }
                test.equal(5, numberEqual);
                done();
              });
          });
        }

        insert(function () {
          finished();
        });
      });
    }
  });

  it('shouldCorrectlyHandleLimitSkipChainingInline', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_limit_skip_chaining_inline', (err, collection) => {
          expect(err).to.not.exist;

          function insert(callback) {
            var total = 10;

            for (var i = 0; i < 10; i++) {
              collection.insert({ x: i }, configuration.writeConcernMax(), e => {
                expect(e).to.not.exist;
                total = total - 1;
                if (total === 0) callback();
              });
            }
          }

          function finished() {
            collection.find().toArray((err, items) => {
              expect(err).to.not.exist;
              test.equal(10, items.length);

              collection
                .find()
                .limit(5)
                .skip(3)
                .toArray(function (err, items2) {
                  expect(err).to.not.exist;
                  test.equal(5, items2.length);

                  // Check that we have the same elements
                  var numberEqual = 0;
                  var sliced = items.slice(3, 8);

                  for (var i = 0; i < sliced.length; i++) {
                    if (sliced[i].x === items2[i].x) numberEqual = numberEqual + 1;
                  }
                  test.equal(5, numberEqual);
                  done();
                });
            });
          }

          insert(function () {
            finished();
          });
        });
      });
    }
  });

  it('shouldCloseCursorNoQuerySent', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_close_no_query_sent', (err, collection) => {
          expect(err).to.not.exist;

          const cursor = collection.find();
          cursor.close(err => {
            expect(err).to.not.exist;
            test.equal(true, cursor.closed);
            done();
          });
        });
      });
    }
  });

  it('shouldCorrectlyRefillViaGetMoreCommand', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var COUNT = 1000;

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_refill_via_get_more', (err, collection) => {
          expect(err).to.not.exist;

          function insert(callback) {
            var docs = [];

            for (var i = 0; i < COUNT; i++) {
              docs.push({ a: i });
            }

            collection.insertMany(docs, configuration.writeConcernMax(), callback);
          }

          function finished() {
            collection.count((err, count) => {
              expect(err).to.not.exist;
              test.equal(COUNT, count);
            });

            var total = 0;
            collection.find({}, {}).forEach(
              item => {
                total = total + item.a;
              },
              err => {
                expect(err).to.not.exist;
                test.equal(499500, total);

                collection.count((err, count) => {
                  expect(err).to.not.exist;
                  test.equal(COUNT, count);
                });

                collection.count((err, count) => {
                  expect(err).to.not.exist;
                  test.equal(COUNT, count);

                  var total2 = 0;
                  collection.find().forEach(
                    item => {
                      total2 = total2 + item.a;
                    },
                    err => {
                      expect(err).to.not.exist;
                      test.equal(499500, total2);
                      collection.count((err, count) => {
                        expect(err).to.not.exist;
                        test.equal(COUNT, count);
                        test.equal(total, total2);
                        done();
                      });
                    }
                  );
                });
              }
            );
          }

          insert(function () {
            finished();
          });
        });
      });
    }
  });

  it('shouldCorrectlyRefillViaGetMoreAlternativeCollection', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_refill_via_get_more_alt_coll', (err, collection) => {
          expect(err).to.not.exist;
          var COUNT = 1000;

          function insert(callback) {
            var docs = [];

            for (var i = 0; i < COUNT; i++) {
              docs.push({ a: i });
            }

            collection.insertMany(docs, configuration.writeConcernMax(), callback);
          }

          function finished() {
            collection.count((err, count) => {
              expect(err).to.not.exist;
              test.equal(1000, count);
            });

            var total = 0;
            collection.find().forEach(
              doc => {
                total = total + doc.a;
              },
              err => {
                expect(err).to.not.exist;
                test.equal(499500, total);

                collection.count((err, count) => {
                  expect(err).to.not.exist;
                  test.equal(1000, count);
                });

                collection.count((err, count) => {
                  expect(err).to.not.exist;
                  test.equal(1000, count);

                  var total2 = 0;
                  collection.find().forEach(
                    doc => {
                      total2 = total2 + doc.a;
                    },
                    err => {
                      expect(err).to.not.exist;
                      expect(total2).to.equal(499500);

                      collection.count((err, count) => {
                        expect(err).to.not.exist;
                        expect(count).to.equal(1000);
                        expect(total2).to.equal(total);
                        done();
                      });
                    }
                  );
                });
              }
            );
          }

          insert(function () {
            finished();
          });
        });
      });
    }
  });

  it('shouldCloseCursorAfterQueryHasBeenSent', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_close_after_query_sent', (err, collection) => {
          expect(err).to.not.exist;

          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            const cursor = collection.find({ a: 1 });
            cursor.next(err => {
              expect(err).to.not.exist;

              cursor.close(err => {
                expect(err).to.not.exist;
                test.equal(true, cursor.closed);
                done();
              });
            });
          });
        });
      });
    }
  });

  it('shouldCorrectlyExecuteCursorCountWithFields', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_count_with_fields', (err, collection) => {
          expect(err).to.not.exist;

          collection.insertOne({ x: 1, a: 2 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            collection
              .find({})
              .project({ a: 1 })
              .toArray((err, items) => {
                expect(err).to.not.exist;
                test.equal(1, items.length);
                test.equal(2, items[0].a);
                expect(items[0].x).to.not.exist;
                done();
              });
          });
        });
      });
    }
  });

  it('shouldCorrectlyCountWithFieldsUsingExclude', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('test_count_with_fields_using_exclude', (err, collection) => {
          expect(err).to.not.exist;

          collection.insertOne({ x: 1, a: 2 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            collection.find({}, { projection: { x: 0 } }).toArray((err, items) => {
              expect(err).to.not.exist;
              test.equal(1, items.length);
              test.equal(2, items[0].a);
              expect(items[0].x).to.not.exist;
              done();
            });
          });
        });
      });
    }
  });

  it('Should correctly execute count on cursor', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('Should_correctly_execute_count_on_cursor_1', (err, collection) => {
          expect(err).to.not.exist;

          // insert all docs
          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            let total = 0;
            // Create a cursor for the content
            const cursor = collection.find({});
            this.defer(() => cursor.close());

            cursor.count(err => {
              expect(err).to.not.exist;
              // Ensure each returns all documents
              cursor.forEach(
                () => {
                  total++;
                },
                err => {
                  expect(err).to.not.exist;
                  cursor.count((err, c) => {
                    expect(err).to.not.exist;
                    expect(c).to.equal(1000);
                    expect(total).to.equal(1000);
                    done();
                  });
                }
              );
            });
          });
        });
      });
    }
  });

  it('does not auto destroy streams', function (done) {
    const docs = [];

    for (var i = 0; i < 10; i++) {
      docs.push({ a: i + 1 });
    }

    const configuration = this.configuration;
    client.connect((err, client) => {
      expect(err).to.not.exist;

      const db = client.db(configuration.db);
      db.createCollection('does_not_autodestroy_streams', (err, collection) => {
        expect(err).to.not.exist;

        collection.insertMany(docs, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          const cursor = collection.find();
          const stream = cursor.stream();
          stream.on('close', () => {
            expect.fail('extra close event must not be called');
          });
          stream.on('end', () => {
            client.close();
            done();
          });
          stream.on('data', doc => {
            expect(doc).to.exist;
          });
          stream.resume();
        });
      });
    });
  });

  it('should be able to stream documents', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        docs[i] = { a: i + 1 };
      }

      var count = 0;

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('Should_be_able_to_stream_documents', (err, collection) => {
          expect(err).to.not.exist;

          // insert all docs
          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            var paused = 0,
              closed = 0,
              resumed = 0,
              i = 0;

            const cursor = collection.find();
            const stream = cursor.stream();

            stream.on('data', function (doc) {
              test.equal(true, !!doc);
              test.equal(true, !!doc.a);
              count = count + 1;

              if (paused > 0 && 0 === resumed) {
                err = new Error('data emitted during pause');
                return testDone();
              }

              if (++i === 3) {
                stream.pause();
                paused++;

                setTimeout(function () {
                  stream.resume();
                  resumed++;
                }, 20);
              }
            });

            stream.once('error', function (er) {
              err = er;
              testDone();
            });

            stream.once('end', function () {
              closed++;
              testDone();
            });

            function testDone() {
              expect(err).to.not.exist;
              test.equal(i, docs.length);
              test.equal(1, closed);
              test.equal(1, paused);
              test.equal(1, resumed);
              test.strictEqual(cursor.closed, true);
              done();
            }
          });
        });
      });
    }
  });

  it('immediately destroying a stream prevents the query from executing', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var i = 0,
        docs = [{ b: 2 }, { b: 3 }],
        doneCalled = 0;

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection(
          'immediately_destroying_a_stream_prevents_the_query_from_executing',
          (err, collection) => {
            expect(err).to.not.exist;

            // insert all docs
            collection.insertMany(docs, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;

              const cursor = collection.find();
              const stream = cursor.stream();

              stream.on('data', function () {
                i++;
              });

              cursor.once('close', testDone('close'));
              stream.once('error', testDone('error'));

              stream.destroy();

              function testDone() {
                return err => {
                  ++doneCalled;

                  if (doneCalled === 1) {
                    expect(err).to.not.exist;
                    test.strictEqual(0, i);
                    test.strictEqual(true, cursor.closed);
                    done();
                  }
                };
              }
            });
          }
        );
      });
    }
  });

  it('removes session when cloning an find cursor', async function () {
    const collection = await client.db().collection('test');

    const cursor = collection.find({});
    const clonedCursor = cursor.clone();

    expect(cursor).to.have.property('session');
    expect(clonedCursor).to.have.property('session');
    expect(cursor.session).to.not.equal(clonedCursor.session);
  });

  it('removes session when cloning an aggregation cursor', async function () {
    const collection = await client.db().collection('test');

    const cursor = collection.aggregate([{ $match: {} }]);
    const clonedCursor = cursor.clone();

    expect(cursor).to.have.property('session');
    expect(clonedCursor).to.have.property('session');
    expect(cursor.session).to.not.equal(clonedCursor.session);
  });

  it('destroying a stream stops it', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('destroying_a_stream_stops_it', (err, collection) => {
          expect(err).to.not.exist;

          var docs = [];
          for (var ii = 0; ii < 10; ++ii) docs.push({ b: ii + 1 });

          // insert all docs
          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            var finished = 0,
              i = 0;

            const cursor = collection.find();
            const stream = cursor.stream();

            test.strictEqual(false, cursor.closed);

            stream.on('data', function () {
              if (++i === 5) {
                stream.destroy();
              }
            });

            cursor.once('close', testDone);
            stream.once('error', testDone);
            stream.once('end', testDone);

            function testDone(err) {
              ++finished;
              if (finished === 2) {
                test.strictEqual(undefined, err);
                test.strictEqual(5, i);
                test.strictEqual(2, finished);
                test.strictEqual(true, cursor.closed);
                done();
              }
            }
          });
        });
      });
    }
  });

  // NOTE: skipped for use of topology manager
  it.skip('cursor stream errors', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: { requires: { topology: ['single'] } },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('cursor_stream_errors', (err, collection) => {
          expect(err).to.not.exist;

          var docs = [];
          for (var ii = 0; ii < 10; ++ii) docs.push({ b: ii + 1 });

          // insert all docs
          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            var finished = 0,
              i = 0;

            const cursor = collection.find({}, { batchSize: 5 });
            const stream = cursor.stream();

            stream.on('data', function () {
              if (++i === 4) {
                // Force restart
                configuration.manager.stop(9);
              }
            });

            stream.once('close', testDone('close'));
            stream.once('error', testDone('error'));

            function testDone() {
              return function () {
                ++finished;

                if (finished === 2) {
                  setTimeout(function () {
                    test.equal(5, i);
                    test.equal(true, cursor.closed);
                    client.close();

                    configuration.manager.start().then(function () {
                      done();
                    });
                  }, 150);
                }
              };
            }
          });
        });
      });
    }
  });

  it('cursor stream pipe', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('cursor_stream_pipe', (err, collection) => {
          expect(err).to.not.exist;

          var docs = [];
          'Aaden Aaron Adrian Aditya Bob Joe'.split(' ').forEach(function (name) {
            docs.push({ name: name });
          });

          // insert all docs
          collection.insertMany(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            const filename = path.join(os.tmpdir(), '_nodemongodbnative_stream_out.txt');
            const out = fs.createWriteStream(filename);
            const stream = collection.find().stream({
              transform: doc => JSON.stringify(doc)
            });

            stream.pipe(out);
            // Wait for output stream to close
            out.on('close', testDone);

            function testDone(err) {
              // Object.prototype.toString = toString;
              test.strictEqual(undefined, err);
              var contents = fs.readFileSync(filename, 'utf8');
              test.ok(/Aaden/.test(contents));
              test.ok(/Aaron/.test(contents));
              test.ok(/Adrian/.test(contents));
              test.ok(/Aditya/.test(contents));
              test.ok(/Bob/.test(contents));
              test.ok(/Joe/.test(contents));
              fs.unlinkSync(filename);
              done();
            }
          });
        });
      });
    }
  });

  it('should close dead tailable cursors', {
    metadata: {
      os: '!win32' // NODE-2943: timeout on windows
    },

    test: function (done) {
      // http://www.mongodb.org/display/DOCS/Tailable+Cursors

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        const options = { capped: true, size: 10000000 };
        db.createCollection(
          'test_if_dead_tailable_cursors_close',
          options,
          function (err, collection) {
            expect(err).to.not.exist;

            let closeCount = 0;
            const docs = Array.from({ length: 100 }).map(() => ({ a: 1 }));
            collection.insertMany(docs, { w: 'majority', wtimeoutMS: 5000 }, err => {
              expect(err).to.not.exist;

              const cursor = collection.find({}, { tailable: true, awaitData: true });
              const stream = cursor.stream();

              stream.resume();

              var validator = () => {
                closeCount++;
                if (closeCount === 2) {
                  done();
                }
              };

              // we validate that the stream "ends" either cleanly or with an error
              stream.on('end', validator);
              stream.on('error', validator);

              cursor.on('close', validator);

              const docs = Array.from({ length: 100 }).map(() => ({ a: 1 }));
              collection.insertMany(docs, err => {
                expect(err).to.not.exist;

                setTimeout(() => client.close());
              });
            });
          }
        );
      });
    }
  });

  it('shouldAwaitData', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      // http://www.mongodb.org/display/DOCS/Tailable+Cursors

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        const options = { capped: true, size: 8 };
        db.createCollection(
          'should_await_data_retry_tailable_cursor',
          options,
          (err, collection) => {
            expect(err).to.not.exist;

            collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;

              // Create cursor with awaitData, and timeout after the period specified
              const cursor = collection.find({}, { tailable: true, awaitData: true });
              this.defer(() => cursor.close());

              // Execute each
              cursor.forEach(
                () => cursor.close(),
                () => {
                  // Even though cursor is exhausted, should not close session
                  // unless cursor is manually closed, due to awaitData / tailable
                  done();
                }
              );
            });
          }
        );
      });
    }
  });

  it('shouldAwaitDataWithDocumentsAvailable', function (done) {
    // http://www.mongodb.org/display/DOCS/Tailable+Cursors

    const configuration = this.configuration;
    const client = configuration.newClient({ maxPoolSize: 1 });
    client.connect((err, client) => {
      expect(err).to.not.exist;
      this.defer(() => client.close());

      const db = client.db(configuration.db);
      const options = { capped: true, size: 8 };
      db.createCollection('should_await_data_no_docs', options, (err, collection) => {
        expect(err).to.not.exist;

        // Create cursor with awaitData, and timeout after the period specified
        const cursor = collection.find({}, { tailable: true, awaitData: true });
        this.defer(() => cursor.close());

        cursor.forEach(
          () => {},
          err => {
            expect(err).to.not.exist;
            done();
          }
        );
      });
    });
  });

  context('awaiting data core tailable cursor test', () => {
    let client;
    let cursor;

    beforeEach(async function () {
      client = await this.configuration.newClient().connect();
    });

    afterEach(async () => {
      if (cursor) await cursor.close();
      await client.close();
    });

    it(
      'should block waiting for new data to arrive when the cursor reaches the end of the capped collection',
      {
        metadata: { requires: { mongodb: '>=3.2' } },
        async test() {
          const db = client.db('cursor_tailable');

          try {
            await db.collection('cursor_tailable').drop();
            // eslint-disable-next-line no-empty
          } catch (_) {}

          const collection = await db.createCollection('cursor_tailable', {
            capped: true,
            size: 10000
          });

          const res = await collection.insertOne({ a: 1 });
          expect(res).property('insertedId').to.exist;

          cursor = collection.find({}, { batchSize: 2, tailable: true, awaitData: true });
          const doc0 = await cursor.next();
          expect(doc0).to.have.property('a', 1);

          // After 300ms make an insert
          const later = runLater(async () => {
            const res = await collection.insertOne({ b: 2 });
            expect(res).property('insertedId').to.exist;
          }, 300);

          const start = new Date();
          const doc1 = await cursor.next();
          expect(doc1).to.have.property('b', 2);
          const end = new Date();

          await later; // make sure this finished, without a failure

          // We should see here that cursor.next blocked for at least 300ms
          expect(end.getTime() - start.getTime()).to.be.at.least(300);
        }
      }
    );
  });

  // NOTE: should we continue to let users explicitly `kill` a cursor?
  it.skip('Should correctly retry tailable cursor connection', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      // http://www.mongodb.org/display/DOCS/Tailable+Cursors

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        const options = { capped: true, size: 8 };
        db.createCollection('should_await_data', options, (err, collection) => {
          expect(err).to.not.exist;

          collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            // Create cursor with awaitData, and timeout after the period specified
            var cursor = collection.find({}, { tailable: true, awaitData: true });
            cursor.forEach(
              () => cursor.kill(),
              () => {
                // kill cursor b/c cursor is tailable / awaitable
                cursor.close(done);
              }
            );
          });
        });
      });
    }
  });

  it('shouldCorrectExecuteExplainHonoringLimit', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];
      docs[0] = {
        _keywords: [
          'compact',
          'ii2gd',
          'led',
          '24-48v',
          'presse-etoupe',
          'bexbgl1d24483',
          'flash',
          '48v',
          'eexd',
          'feu',
          'presse',
          'compris',
          'rouge',
          'etoupe',
          'iic',
          'ii2gdeexdiict5',
          'red',
          'aet'
        ]
      };
      docs[1] = {
        _keywords: [
          'reducteur',
          '06212',
          'd20/16',
          'manch',
          'd20',
          'manchon',
          'ard',
          'sable',
          'irl',
          'red'
        ]
      };
      docs[2] = {
        _keywords: [
          'reducteur',
          '06214',
          'manch',
          'd25/20',
          'd25',
          'manchon',
          'ard',
          'sable',
          'irl',
          'red'
        ]
      };
      docs[3] = {
        _keywords: [
          'bar',
          'rac',
          'boite',
          '6790178',
          '50-240/4-35',
          '240',
          'branch',
          'coulee',
          'ddc',
          'red',
          'ip2x'
        ]
      };
      docs[4] = {
        _keywords: [
          'bar',
          'ip2x',
          'boite',
          '6790158',
          'ddi',
          '240',
          'branch',
          'injectee',
          '50-240/4-35?',
          'red'
        ]
      };
      docs[5] = {
        _keywords: [
          'bar',
          'ip2x',
          'boite',
          '6790179',
          'coulee',
          '240',
          'branch',
          'sdc',
          '50-240/4-35?',
          'red',
          'rac'
        ]
      };
      docs[6] = {
        _keywords: [
          'bar',
          'ip2x',
          'boite',
          '6790159',
          '240',
          'branch',
          'injectee',
          '50-240/4-35?',
          'sdi',
          'red'
        ]
      };
      docs[7] = {
        _keywords: [
          '6000',
          'r-6000',
          'resin',
          'high',
          '739680',
          'red',
          'performance',
          'brd',
          'with',
          'ribbon',
          'flanges'
        ]
      };
      docs[8] = { _keywords: ['804320', 'for', 'paint', 'roads', 'brd', 'red'] };
      docs[9] = { _keywords: ['38mm', 'padlock', 'safety', '813594', 'brd', 'red'] };
      docs[10] = { _keywords: ['114551', 'r6900', 'for', 'red', 'bmp71', 'brd', 'ribbon'] };
      docs[11] = {
        _keywords: ['catena', 'diameter', '621482', 'rings', 'brd', 'legend', 'red', '2mm']
      };
      docs[12] = {
        _keywords: ['catena', 'diameter', '621491', 'rings', '5mm', 'brd', 'legend', 'red']
      };
      docs[13] = {
        _keywords: ['catena', 'diameter', '621499', 'rings', '3mm', 'brd', 'legend', 'red']
      };
      docs[14] = {
        _keywords: ['catena', 'diameter', '621508', 'rings', '5mm', 'brd', 'legend', 'red']
      };
      docs[15] = {
        _keywords: [
          'insert',
          'for',
          'cable',
          '3mm',
          'carrier',
          '621540',
          'blank',
          'brd',
          'ademark',
          'red'
        ]
      };
      docs[16] = {
        _keywords: [
          'insert',
          'for',
          'cable',
          '621544',
          '3mm',
          'carrier',
          'brd',
          'ademark',
          'legend',
          'red'
        ]
      };
      docs[17] = {
        _keywords: ['catena', 'diameter', '6mm', '621518', 'rings', 'brd', 'legend', 'red']
      };
      docs[18] = {
        _keywords: ['catena', 'diameter', '621455', '8mm', 'rings', 'brd', 'legend', 'red']
      };
      docs[19] = {
        _keywords: ['catena', 'diameter', '621464', 'rings', '5mm', 'brd', 'legend', 'red']
      };

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        // Insert all the docs
        var collection = db.collection('shouldCorrectExecuteExplainHonoringLimit');
        collection.insert(docs, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          collection.createIndex({ _keywords: 1 }, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            collection
              .find({ _keywords: 'red' })
              .limit(10)
              .toArray(function (err, result) {
                expect(err).to.not.exist;
                test.ok(result != null);

                collection
                  .find({ _keywords: 'red' }, {})
                  .limit(10)
                  .explain(function (err, result) {
                    expect(err).to.not.exist;
                    test.ok(result != null);

                    done();
                  });
              });
          });
        });
      });
    }
  });

  it('shouldNotExplainWhenFalse', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var doc = { name: 'camera', _keywords: ['compact', 'ii2gd', 'led', 'red', 'aet'] };

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var collection = db.collection('shouldNotExplainWhenFalse');
        collection.insert(doc, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          collection
            .find({ _keywords: 'red' })
            .limit(10)
            .toArray(function (err, result) {
              expect(err).to.not.exist;

              test.equal('camera', result[0].name);
              done();
            });
        });
      });
    }
  });

  it('shouldFailToSetReadPreferenceOnCursor', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        try {
          db.collection('shouldFailToSetReadPreferenceOnCursor')
            .find()
            .withReadPreference('notsecondary');
          test.ok(false);
        } catch (err) {} // eslint-disable-line

        db.collection('shouldFailToSetReadPreferenceOnCursor')
          .find()
          .withReadPreference('secondary');

        done();
      });
    }
  });

  it('should allow setting the cursors readConcern through a builder', {
    metadata: { requires: { mongodb: '>=3.2' } },
    test: function (done) {
      const client = this.configuration.newClient({ monitorCommands: true });
      const events = [];
      client.on('commandStarted', event => {
        if (event.commandName === 'find') {
          events.push(event);
        }
      });
      const db = client.db(this.configuration.db);
      const cursor = db.collection('foo').find().withReadConcern('local');
      expect(cursor).property('readConcern').to.have.property('level').equal('local');

      cursor.toArray(err => {
        expect(err).to.not.exist;

        expect(events).to.have.length(1);
        const findCommand = events[0];
        expect(findCommand).nested.property('command.readConcern').to.eql({ level: 'local' });
        client.close(done);
      });
    }
  });

  it('shouldNotFailDueToStackOverflowEach', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('shouldNotFailDueToStackOverflowEach', (err, collection) => {
          expect(err).to.not.exist;

          var docs = [];
          var total = 0;
          for (var i = 0; i < 30000; i++) docs.push({ a: i });
          var allDocs = [];
          var left = 0;

          while (docs.length > 0) {
            allDocs.push(docs.splice(0, 1000));
          }
          // Get all batches we must insert
          left = allDocs.length;
          var totalI = 0;

          // Execute inserts
          for (i = 0; i < left; i++) {
            collection.insert(allDocs.shift(), configuration.writeConcernMax(), function (err, d) {
              expect(err).to.not.exist;

              left = left - 1;
              totalI = totalI + d.length;

              if (left === 0) {
                collection.find({}).forEach(
                  () => {
                    total++;
                  },
                  err => {
                    expect(err).to.not.exist;
                    expect(total).to.equal(30000);
                    done();
                  }
                );
              }
            });
          }
        });
      });
    }
  });

  it('should not fail due to stack overflow toArray', async function () {
    const configuration = this.configuration;
    const db = client.db(configuration.db);
    const collection = await db.createCollection('shouldNotFailDueToStackOverflowToArray');

    var docs = Array.from({ length: 30000 }, (_, i) => ({ a: i }));
    var allDocs = [];
    var left = 0;

    while (docs.length > 0) {
      allDocs.push(docs.splice(0, 1000));
    }
    // Get all batches we must insert
    left = allDocs.length;
    var totalI = 0;
    var timeout = 0;

    // Execute inserts
    for (let i = 0; i < left; i++) {
      await sleep(timeout);

      const d = await collection.insert(allDocs.shift());
      left = left - 1;
      totalI = totalI + d.length;

      if (left === 0) {
        const items = await collection.find({}).toArray();
        expect(items).to.have.a.lengthOf(3000);
      }
      timeout = timeout + 100;
    }

    await client.close();
  });

  it('should correctly skip and limit', function (done) {
    const configuration = this.configuration;
    client.connect((err, client) => {
      expect(err).to.not.exist;

      const db = client.db(configuration.db);
      var collection = db.collection('shouldCorrectlySkipAndLimit');
      var docs = [];
      for (var i = 0; i < 100; i++) docs.push({ a: i, OrderNumber: i });

      collection.insert(docs, configuration.writeConcernMax(), err => {
        expect(err).to.not.exist;

        collection
          .find({}, { OrderNumber: 1 })
          .skip(10)
          .limit(10)
          .toArray((err, items) => {
            expect(err).to.not.exist;
            test.equal(10, items[0].OrderNumber);

            collection
              .find({}, { OrderNumber: 1 })
              .skip(10)
              .limit(10)
              .count()
              .then(count => {
                test.equal(10, count);
                client.close(done);
              });
          });
      });
    });
  });

  it('shouldFailToTailANormalCollection', function (done) {
    const configuration = this.configuration;
    client.connect((err, client) => {
      expect(err).to.not.exist;
      this.defer(() => client.close());

      const db = client.db(configuration.db);
      var collection = db.collection('shouldFailToTailANormalCollection');
      var docs = [];
      for (var i = 0; i < 100; i++) docs.push({ a: i, OrderNumber: i });

      collection.insert(docs, configuration.writeConcernMax(), err => {
        expect(err).to.not.exist;

        const cursor = collection.find({}, { tailable: true });
        cursor.forEach(
          () => {},
          err => {
            test.ok(err instanceof Error);
            test.ok(typeof err.code === 'number');

            // Close cursor b/c we did not exhaust cursor
            cursor.close();
            done();
          }
        );
      });
    });
  });

  it('shouldCorrectlyUseFindAndCursorCount', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;

      // DOC_LINE var client = new MongoClient(new Server('localhost', 27017));
      // DOC_START
      // Establish connection to db
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);

        // Create a lot of documents to insert
        var docs = [];
        for (var i = 0; i < 100; i++) {
          docs.push({ a: i });
        }

        // Create a collection
        db.createCollection('test_close_function_on_cursor_2', (err, collection) => {
          expect(err).to.not.exist;

          // Insert documents into collection
          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            const cursor = collection.find({});

            cursor.count((err, count) => {
              expect(err).to.not.exist;
              test.equal(100, count);

              done();
            });
          });
        });
      });
      // DOC_END
    }
  });

  it('should correctly apply hint to count command for cursor', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: {
        topology: ['single', 'replicaset', 'sharded'],
        mongodb: '>2.5.5'
      }
    },

    test: function (done) {
      const configuration = this.configuration;

      // DOC_LINE var client = new MongoClient(new Server('localhost', 27017));
      // DOC_START
      // Establish connection to db
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var col = db.collection('count_hint');

        col.insert([{ i: 1 }, { i: 2 }], { writeConcern: { w: 1 } }, err => {
          expect(err).to.not.exist;

          col.createIndex({ i: 1 }, err => {
            expect(err).to.not.exist;

            col.find({ i: 1 }, { hint: '_id_' }).count((err, count) => {
              expect(err).to.not.exist;
              test.equal(1, count);

              col.find({}, { hint: '_id_' }).count((err, count) => {
                expect(err).to.not.exist;
                test.equal(2, count);

                col.find({ i: 1 }, { hint: 'BAD HINT' }).count(err => {
                  test.ok(err != null);

                  col.createIndex({ x: 1 }, { sparse: true }, err => {
                    expect(err).to.not.exist;

                    col.find({ i: 1 }, { hint: 'x_1' }).count((err, count) => {
                      expect(err).to.not.exist;
                      test.equal(0, count);

                      col.find({}, { hint: 'i_1' }).count((err, count) => {
                        expect(err).to.not.exist;
                        test.equal(2, count);

                        done();
                      });
                    });
                  });
                });
              });
            });
          });
        });
      });
      // DOC_END
    }
  });

  it('Terminate each after first document by returning false', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);

        // Create a lot of documents to insert
        var docs = [];
        for (var i = 0; i < 100; i++) {
          docs.push({ a: i });
        }

        // Create a collection
        db.createCollection('terminate_each_returning_false', (err, collection) => {
          expect(err).to.not.exist;

          // Insert documents into collection
          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;
            var finished = false;

            collection.find({}).forEach(
              doc => {
                expect(doc).to.exist;
                test.equal(finished, false);
                finished = true;

                done();
                return false;
              },
              err => {
                expect(err).to.not.exist;
              }
            );
          });
        });
      });
    }
  });

  it('Should correctly handle maxTimeMS as part of findOne options', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var donkey = {
          color: 'brown'
        };

        db.collection('donkies').insertOne(donkey, function (err, result) {
          expect(err).to.not.exist;

          var query = { _id: result.insertedId };
          var options = { maxTimeMS: 1000 };

          db.collection('donkies').findOne(query, options, function (err, doc) {
            expect(err).to.not.exist;
            test.equal('brown', doc.color);

            done();
          });
        });
      });
    }
  });

  it('Should correctly handle batchSize of 2', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        const collectionName = 'should_correctly_handle_batchSize_2';
        db.collection(collectionName).insert([{ x: 1 }, { x: 2 }, { x: 3 }], err => {
          expect(err).to.not.exist;

          const cursor = db.collection(collectionName).find({}, { batchSize: 2 });
          this.defer(() => cursor.close());

          cursor.next(err => {
            expect(err).to.not.exist;

            cursor.next(err => {
              expect(err).to.not.exist;

              cursor.next(err => {
                expect(err).to.not.exist;
                done();
              });
            });
          });
        });
      });
    }
  });

  it('Should report database name and collection name', {
    metadata: { requires: { topology: ['single'] } },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        const cursor = db.collection('myCollection').find({});
        test.equal('myCollection', cursor.namespace.collection);
        test.equal('integration_tests', cursor.namespace.db);

        done();
      });
    }
  });

  it('Should correctly execute count on cursor with maxTimeMS', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection(
          'Should_correctly_execute_count_on_cursor_2',
          function (err, collection) {
            expect(err).to.not.exist;

            // insert all docs
            collection.insert(docs, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;

              // Create a cursor for the content
              var cursor = collection.find({});
              cursor.limit(100);
              cursor.skip(10);
              cursor.count({ maxTimeMS: 1000 }, err => {
                expect(err).to.not.exist;

                // Create a cursor for the content
                var cursor = collection.find({});
                cursor.limit(100);
                cursor.skip(10);
                cursor.maxTimeMS(100);

                cursor.count(err => {
                  expect(err).to.not.exist;
                  done();
                });
              });
            });
          }
        );
      });
    }
  });

  it('Should correctly execute count on cursor with maxTimeMS set using legacy method', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection(
          'Should_correctly_execute_count_on_cursor_3',
          function (err, collection) {
            expect(err).to.not.exist;

            // insert all docs
            collection.insert(docs, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;

              // Create a cursor for the content
              var cursor = collection.find({}, { maxTimeMS: 100 });
              cursor.toArray(err => {
                expect(err).to.not.exist;

                done();
              });
            });
          }
        );
      });
    }
  });

  it('Should correctly apply map to toArray', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var collection = db.collection('map_toArray');

        // insert all docs
        collection.insert(docs, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          // Create a cursor for the content
          var cursor = collection
            .find({})
            .map(function () {
              return { a: 1 };
            })
            .batchSize(5)
            .limit(10);

          cursor.toArray(function (err, docs) {
            expect(err).to.not.exist;
            test.equal(10, docs.length);

            // Ensure all docs where mapped
            docs.forEach(doc => {
              expect(doc).property('a').to.equal(1);
            });

            done();
          });
        });
      });
    }
  });

  it('Should correctly apply map to next', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      const docs = [];
      for (var i = 0; i < 1000; i++) {
        const d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        const collection = db.collection('map_next');

        // insert all docs
        collection.insert(docs, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          // Create a cursor for the content
          const cursor = collection
            .find({})
            .map(function () {
              return { a: 1 };
            })
            .batchSize(5)
            .limit(10);

          this.defer(() => cursor.close());
          cursor.next((err, doc) => {
            expect(err).to.not.exist;
            test.equal(1, doc.a);
            done();
          });
        });
      });
    }
  });

  it('Should correctly apply map to each', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        const collection = db.collection('map_each');

        // insert all docs
        collection.insert(docs, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          // Create a cursor for the content
          var cursor = collection
            .find({})
            .map(function () {
              return { a: 1 };
            })
            .batchSize(5)
            .limit(10);

          cursor.forEach(
            doc => {
              test.equal(1, doc.a);
            },
            err => {
              expect(err).to.not.exist;
              done();
            }
          );
        });
      });
    }
  });

  it('Should correctly apply map to forEach', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var collection = db.collection('map_forEach');

        // insert all docs
        collection.insert(docs, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          // Create a cursor for the content
          var cursor = collection
            .find({})
            .map(function () {
              return { a: 2 };
            })
            .map(function (x) {
              return { a: x.a * x.a };
            })
            .batchSize(5)
            .limit(10);

          cursor.forEach(
            doc => {
              test.equal(4, doc.a);
            },
            err => {
              expect(err).to.not.exist;
              done();
            }
          );
        });
      });
    }
  });

  it('Should correctly apply multiple uses of map and apply forEach', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1000; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var collection = db.collection('map_mapmapforEach');

        // insert all docs
        collection.insert(docs, configuration.writeConcernMax(), err => {
          expect(err).to.not.exist;

          // Create a cursor for the content
          var cursor = collection
            .find({})
            .map(function () {
              return { a: 1 };
            })
            .batchSize(5)
            .limit(10);

          cursor.forEach(
            doc => {
              expect(doc).property('a').to.equal(1);
            },
            err => {
              expect(err).to.not.exist;
              done();
            }
          );
        });
      });
    }
  });

  it('Should correctly apply skip and limit to large set of documents', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: { requires: { topology: ['single', 'replicaset'] } },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var collection = db.collection('cursor_limit_skip_correctly');

        // Insert x number of docs
        var ordered = collection.initializeUnorderedBulkOp();

        for (var i = 0; i < 6000; i++) {
          ordered.insert({ a: i });
        }

        ordered.execute({ writeConcern: { w: 1 } }, err => {
          expect(err).to.not.exist;

          // Let's attempt to skip and limit
          collection
            .find({})
            .limit(2016)
            .skip(2016)
            .toArray(function (err, docs) {
              expect(err).to.not.exist;
              test.equal(2016, docs.length);

              done();
            });
        });
      });
    }
  });

  it('should tail cursor using maxAwaitTimeMS for 3.2 or higher', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: { requires: { topology: ['single'], mongodb: '>3.1.9' } },

    test: function (done) {
      const configuration = this.configuration;
      const client = configuration.newClient();
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var options = { capped: true, size: 8 };
        db.createCollection(
          'should_await_data_max_awaittime_ms',
          options,
          function (err, collection) {
            expect(err).to.not.exist;

            collection.insert({ a: 1 }, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;

              // Create cursor with awaitData, and timeout after the period specified
              var cursor = collection
                .find({})
                .addCursorFlag('tailable', true)
                .addCursorFlag('awaitData', true)
                .maxAwaitTimeMS(500);

              const s = new Date();
              cursor.forEach(
                () => {
                  setTimeout(() => cursor.close(), 300);
                },
                () => {
                  test.ok(new Date().getTime() - s.getTime() >= 500);
                  done();
                }
              );
            });
          }
        );
      });
    }
  });

  it('Should not emit any events after close event emitted due to cursor killed', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: { requires: { topology: ['single', 'replicaset'] } },

    test: function (done) {
      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        var collection = db.collection('cursor_limit_skip_correctly');

        // Insert x number of docs
        var ordered = collection.initializeUnorderedBulkOp();

        for (var i = 0; i < 100; i++) {
          ordered.insert({ a: i });
        }

        ordered.execute({ writeConcern: { w: 1 } }, err => {
          expect(err).to.not.exist;

          // Let's attempt to skip and limit
          var cursor = collection.find({}).batchSize(10);
          const stream = cursor.stream();
          stream.on('data', function () {
            stream.destroy();
          });

          cursor.on('close', function () {
            done();
          });
        });
      });
    }
  });

  it('shouldCorrectlyExecuteEnsureIndexWithNoCallback', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 1; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection(
          'shouldCorrectlyExecuteEnsureIndexWithNoCallback',
          function (err, collection) {
            expect(err).to.not.exist;

            // ensure index of createdAt index
            collection.createIndex({ createdAt: 1 }, err => {
              expect(err).to.not.exist;

              // insert all docs
              collection.insert(docs, configuration.writeConcernMax(), err => {
                expect(err).to.not.exist;

                // Find with sort
                collection
                  .find()
                  .sort(['createdAt', 'asc'])
                  .toArray((err, items) => {
                    expect(err).to.not.exist;

                    test.equal(1, items.length);
                    done();
                  });
              });
            });
          }
        );
      });
    }
  });

  it('Should correctly execute count on cursor with limit and skip', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];

      for (var i = 0; i < 50; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      const configuration = this.configuration;
      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection('negative_batch_size_and_limit_set', (err, collection) => {
          expect(err).to.not.exist;

          // insert all docs
          collection.insert(docs, configuration.writeConcernMax(), err => {
            expect(err).to.not.exist;

            // Create a cursor for the content
            var cursor = collection.find({});
            cursor
              .limit(100)
              .skip(0)
              .count(function (err, c) {
                expect(err).to.not.exist;
                test.equal(50, c);

                var cursor = collection.find({});
                cursor
                  .limit(100)
                  .skip(0)
                  .toArray(err => {
                    expect(err).to.not.exist;
                    test.equal(50, c);

                    done();
                  });
              });
          });
        });
      });
    }
  });

  it('Should correctly handle negative batchSize and set the limit', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var docs = [];
      const configuration = this.configuration;

      for (var i = 0; i < 50; i++) {
        var d = new Date().getTime() + i * 1000;
        docs[i] = { a: i, createdAt: new Date(d) };
      }

      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.createCollection(
          'Should_correctly_execute_count_on_cursor_1_',
          function (err, collection) {
            expect(err).to.not.exist;

            // insert all docs
            collection.insert(docs, configuration.writeConcernMax(), err => {
              expect(err).to.not.exist;

              // Create a cursor for the content
              var cursor = collection.find({});
              cursor.batchSize(-10).next(err => {
                expect(err).to.not.exist;
                test.ok(cursor.id.equals(BSON.Long.ZERO));

                done();
              });
            });
          }
        );
      });
    }
  });

  it('Correctly decorate the cursor count command with skip, limit, hint, readConcern', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var started = [];
      const configuration = this.configuration;
      const client = configuration.newClient(configuration.writeConcernMax(), {
        maxPoolSize: 1,
        monitorCommands: true
      });
      client.on('commandStarted', function (event) {
        if (event.commandName === 'count') started.push(event);
      });

      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.collection('cursor_count_test', { readConcern: { level: 'local' } })
          .find({ project: '123' })
          .limit(5)
          .skip(5)
          .hint({ project: 1 })
          .count(err => {
            expect(err).to.not.exist;
            test.equal(1, started.length);
            if (started[0].command.readConcern)
              test.deepEqual({ level: 'local' }, started[0].command.readConcern);
            test.deepEqual({ project: 1 }, started[0].command.hint);
            test.equal(5, started[0].command.skip);
            test.equal(5, started[0].command.limit);

            done();
          });
      });
    }
  });

  it.skip('Correctly decorate the collection count command with skip, limit, hint, readConcern', {
    // Add a tag that our runner can trigger on
    // in this case we are setting that node needs to be higher than 0.10.X to run
    metadata: {
      requires: { topology: ['single', 'replicaset', 'sharded'] }
    },

    test: function (done) {
      var started = [];

      const configuration = this.configuration;
      client.on('commandStarted', function (event) {
        if (event.commandName === 'count') started.push(event);
      });

      client.connect((err, client) => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const db = client.db(configuration.db);
        db.collection('cursor_count_test1', { readConcern: { level: 'local' } }).count(
          {
            project: '123'
          },
          {
            readConcern: { level: 'local' },
            limit: 5,
            skip: 5,
            hint: { project: 1 }
          },
          err => {
            expect(err).to.not.exist;
            test.equal(1, started.length);
            if (started[0].command.readConcern)
              test.deepEqual({ level: 'local' }, started[0].command.readConcern);
            test.deepEqual({ project: 1 }, started[0].command.hint);
            test.equal(5, started[0].command.skip);
            test.equal(5, started[0].command.limit);

            done();
          }
        );
      });
    }
  });

  // NOTE: should we allow users to explicitly `kill` a cursor anymore?
  it.skip('Should properly kill a cursor', {
    metadata: {
      requires: {
        topology: ['single', 'replicaset', 'sharded'],
        mongodb: '>=3.2.0'
      }
    },

    test: function () {
      // Load up the documents
      const docs = [];
      for (let i = 0; i < 1000; i += 1) {
        docs.push({
          a: i
        });
      }

      const configuration = this.configuration;

      let cleanup = () => {};
      let caughtError = undefined;

      return (
        client
          .connect()
          .then(client => {
            this.defer(() => client.close());
            const db = client.db(configuration.db);
            const collection = db.collection('cursorkilltest1');

            // Insert 1000 documents
            return collection.insert(docs).then(() => {
              // Generate cursor for find operation
              const cursor = collection.find({});
              this.defer(() => cursor.close());

              // Iterate cursor past first element
              return cursor
                .next()
                .then(() => cursor.next())
                .then(() => {
                  // Confirm that cursorId is non-zero
                  const longId = cursor.id;
                  expect(longId).to.be.an('object');
                  expect(Object.getPrototypeOf(longId)).to.haveOwnProperty('_bsontype', 'Long');
                  const id = longId.toNumber();

                  expect(id).to.not.equal(0);

                  // Kill cursor
                  return new Promise((resolve, reject) =>
                    cursor.kill((err, r) => (err ? reject(err) : resolve(r)))
                  ).then(response => {
                    // sharded clusters will return a long, single return integers
                    if (
                      response &&
                      response.cursorsKilled &&
                      Array.isArray(response.cursorsKilled)
                    ) {
                      response.cursorsKilled = response.cursorsKilled.map(id =>
                        typeof id === 'number' ? BSON.Long.fromNumber(id) : id
                      );
                    }

                    expect(response.ok).to.equal(1);
                    expect(response.cursorsKilled[0].equals(longId)).to.be.ok;
                  });
                });
            });
          })

          // Clean up. Make sure that even in case of error, we still always clean up connection
          .catch(e => (caughtError = e))
          .then(cleanup)
          .then(() => {
            if (caughtError) {
              throw caughtError;
            }
          })
      );
    }
  });

  it('should return implicit session to pool when client-side cursor exhausts results on initial query', async function () {
    const configuration = this.configuration;
    const client = configuration.newClient();

    await client.connect();
    const db = client.db(configuration.db);
    const collection = db.collection('cursor_session_tests');

    await collection.insertMany([{ a: 1, b: 2 }]);
    const cursor = collection.find({});

    await cursor.next(); // implicit close, cursor is exhausted
    expect(client.s.activeSessions.size).to.equal(0);
    await cursor.close();
    await client.close();
  });

  it('should return implicit session to pool when client-side cursor exhausts results after a getMore', function (done) {
    const configuration = this.configuration;
    const client = configuration.newClient({ w: 1 }, { maxPoolSize: 1 });

    const db = client.db(configuration.db);
    const collection = db.collection('cursor_session_tests2');

    const docs = [
      { a: 1, b: 2 },
      { a: 3, b: 4 },
      { a: 5, b: 6 },
      { a: 7, b: 8 },
      { a: 9, b: 10 }
    ];

    collection.insertMany(docs, err => {
      expect(err).to.not.exist;
      const cursor = collection.find({}, { batchSize: 3 });
      cursor.next(function () {
        expect(client.s.activeSessions.size).to.equal(1);
        cursor.next(function () {
          expect(client.s.activeSessions.size).to.equal(1);
          cursor.next(function () {
            expect(client.s.activeSessions.size).to.equal(1);
            cursor.next(function () {
              expect(client.s.activeSessions.size).to.equal(0);
              cursor.close(() => {
                client.close(done);
              });
            });
          });
        });
      });
    });
  });

  describe('#clone', function () {
    let client;
    let db;
    let collection;

    beforeEach(function () {
      client = this.configuration.newClient({ w: 1 });

      return client.connect().then(client => {
        db = client.db(this.configuration.db);
        collection = db.collection('test_coll');
      });
    });

    afterEach(function () {
      return client.close();
    });

    context('when executing on a find cursor', function () {
      it('removes the existing session from the cloned cursor', function () {
        const docs = [{ name: 'test1' }, { name: 'test2' }];
        return collection.insertMany(docs).then(() => {
          const cursor = collection.find({}, { batchSize: 1 });
          return cursor
            .next()
            .then(doc => {
              expect(doc).to.exist;
              const clonedCursor = cursor.clone();
              expect(clonedCursor.cursorOptions.session).to.not.exist;
              const kServerSession = getSymbolFrom(clonedCursor.session, 'serverSession');
              expect(clonedCursor.session).to.have.property(kServerSession, null); // session is brand new and has not been used
            })
            .finally(() => {
              return cursor.close();
            });
        });
      });
    });

    context('when executing on an aggregation cursor', function () {
      it('removes the existing session from the cloned cursor', function () {
        const docs = [{ name: 'test1' }, { name: 'test2' }];
        return collection.insertMany(docs).then(() => {
          const cursor = collection.aggregate([{ $match: {} }], { batchSize: 1 });
          return cursor
            .next()
            .then(doc => {
              expect(doc).to.exist;
              const clonedCursor = cursor.clone();
              expect(clonedCursor.cursorOptions.session).to.not.exist;
              const kServerSession = getSymbolFrom(clonedCursor.session, 'serverSession');
              expect(clonedCursor.session).to.have.property(kServerSession, null); // session is brand new and has not been used
            })
            .finally(() => {
              return cursor.close();
            });
        });
      });
    });
  });

  describe('Cursor forEach Error propagation', function () {
    let configuration;
    let client;
    let cursor;
    let collection;

    beforeEach(async function () {
      configuration = this.configuration;
      client = configuration.newClient({ w: 1 }, { maxPoolSize: 1 });
      await client.connect().catch(() => {
        expect.fail('Failed to connect to client');
      });
      collection = client.db(configuration.db).collection('cursor_session_tests2');
    });

    afterEach(async function () {
      await cursor.close();
      await client.close();
    });

    // NODE-2035
    it('should propagate error when exceptions are thrown from an awaited forEach call', async function () {
      const docs = [{ unique_key_2035: 1 }, { unique_key_2035: 2 }, { unique_key_2035: 3 }];
      await collection.insertMany(docs).catch(() => {
        expect.fail('Failed to insert documents');
      });
      cursor = collection.find({
        unique_key_2035: {
          $exists: true
        }
      });
      await cursor
        .forEach(() => {
          throw new Error('FAILURE IN FOREACH CALL');
        })
        .then(() => {
          expect.fail('Error in forEach call not caught');
        })
        .catch(err => {
          expect(err.message).to.deep.equal('FAILURE IN FOREACH CALL');
        });
    });
  });

  it('should return a promise when no callback supplied to forEach method', function () {
    const configuration = this.configuration;
    const client = configuration.newClient({ w: 1 }, { maxPoolSize: 1 });

    return client.connect().then(() => {
      this.defer(() => client.close());

      const db = client.db(configuration.db);
      const collection = db.collection('cursor_session_tests2');
      const cursor = collection.find();
      this.defer(() => cursor.close());

      const promise = cursor.forEach(() => {});
      expect(promise).to.exist.and.to.be.an.instanceof(Promise);
      return promise;
    });
  });

  it('should return false when exhausted and hasNext called more than once', function (done) {
    const configuration = this.configuration;
    const client = configuration.newClient({ w: 1 }, { maxPoolSize: 1 });

    client.connect((err, client) => {
      expect(err).to.not.exist;
      this.defer(() => client.close());

      const db = client.db(configuration.db);
      db.createCollection('cursor_hasNext_test').then(() => {
        const cursor = db.collection('cursor_hasNext_test').find();
        this.defer(() => cursor.close());

        cursor
          .hasNext()
          .then(val1 => {
            expect(val1).to.equal(false);
            return cursor.hasNext();
          })
          .then(val2 => {
            expect(val2).to.equal(false);
            done();
          });
      });
    });
  });

  const testTransformStream = (config, _done) => {
    const client = config.client;
    const configuration = config.configuration;
    const collectionName = config.collectionName;
    const transformFunc = config.transformFunc;
    const expectedSet = config.expectedSet;

    let cursor;
    const done = err => cursor.close(err2 => client.close(err3 => _done(err || err2 || err3)));

    client.connect((err, client) => {
      expect(err).to.not.exist;

      const db = client.db(configuration.db);
      let collection;
      const docs = [
        { _id: 0, a: { b: 1, c: 0 } },
        { _id: 1, a: { b: 1, c: 0 } },
        { _id: 2, a: { b: 1, c: 0 } }
      ];
      const resultSet = new Set();
      const transformParam = transformFunc != null ? { transform: transformFunc } : null;
      Promise.resolve()
        .then(() => db.createCollection(collectionName))
        .then(() => (collection = db.collection(collectionName)))
        .then(() => collection.insertMany(docs))
        .then(() => {
          cursor = collection.find();
          return cursor.stream(transformParam);
        })
        .then(stream => {
          stream.on('data', function (doc) {
            resultSet.add(doc);
          });

          stream.once('end', function () {
            expect(resultSet).to.deep.equal(expectedSet);
            done();
          });

          stream.once('error', e => {
            done(e);
          });
        })
        .catch(e => done(e));
    });
  };

  it('stream should apply the supplied transformation function to each document in the stream', function (done) {
    const configuration = this.configuration;
    const client = configuration.newClient({ w: 1 }, { maxPoolSize: 1 });
    const expectedDocs = [
      { _id: 0, b: 1, c: 0 },
      { _id: 1, b: 1, c: 0 },
      { _id: 2, b: 1, c: 0 }
    ];
    const config = {
      client: client,
      configuration: configuration,
      collectionName: 'stream-test-transform',
      transformFunc: doc => ({ _id: doc._id, b: doc.a.b, c: doc.a.c }),
      expectedSet: new Set(expectedDocs)
    };

    testTransformStream(config, done);
  });

  it('stream should return a stream of unmodified docs if no transform function applied', function (done) {
    const configuration = this.configuration;
    const client = configuration.newClient({ w: 1 }, { maxPoolSize: 1 });
    const expectedDocs = [
      { _id: 0, a: { b: 1, c: 0 } },
      { _id: 1, a: { b: 1, c: 0 } },
      { _id: 2, a: { b: 1, c: 0 } }
    ];
    const config = {
      client: client,
      configuration: configuration,
      collectionName: 'transformStream-test-notransform',
      transformFunc: null,
      expectedSet: new Set(expectedDocs)
    };

    testTransformStream(config, done);
  });

  it.skip('should apply parent read preference to count command', function (done) {
    // NOTE: this test is skipped because mongo orchestration does not test sharded clusters
    // with secondaries. This behavior should be unit tested

    const configuration = this.configuration;
    const client = configuration.newClient(
      { w: 1, readPreference: ReadPreference.SECONDARY },
      { maxPoolSize: 1, connectWithNoPrimary: true }
    );

    client.connect((err, client) => {
      expect(err).to.not.exist;
      this.defer(() => client.close());

      const db = client.db(configuration.db);
      let collection, cursor, spy;
      const close = e => cursor.close(() => client.close(() => done(e)));

      Promise.resolve()
        .then(() => new Promise(resolve => setTimeout(() => resolve(), 500)))
        .then(() => db.createCollection('test_count_readPreference'))
        .then(() => (collection = db.collection('test_count_readPreference')))
        .then(() => collection.find())
        .then(_cursor => (cursor = _cursor))
        .then(() => (spy = sinon.spy(cursor.topology, 'command')))
        .then(() => cursor.count())
        .then(() =>
          expect(spy.firstCall.args[2])
            .to.have.nested.property('readPreference.mode')
            .that.equals('secondary')
        )
        .then(() => close())
        .catch(e => close(e));
    });
  });

  it('should not consume first document on hasNext when streaming', function (done) {
    const configuration = this.configuration;
    const client = configuration.newClient({ w: 1 }, { maxPoolSize: 1 });

    client.connect(err => {
      expect(err).to.not.exist;
      this.defer(() => client.close());

      const collection = client.db().collection('documents');
      collection.drop(() => {
        const docs = [{ a: 1 }, { a: 2 }, { a: 3 }];
        collection.insertMany(docs, err => {
          expect(err).to.not.exist;

          const cursor = collection.find({}, { sort: { a: 1 } });
          cursor.hasNext((err, hasNext) => {
            expect(err).to.not.exist;
            expect(hasNext).to.be.true;

            const collected = [];
            const stream = new Writable({
              objectMode: true,
              write: (chunk, encoding, next) => {
                collected.push(chunk);
                next(undefined, chunk);
              }
            });

            const cursorStream = cursor.stream();

            cursorStream.on('end', () => {
              expect(collected).to.have.length(3);
              expect(collected).to.eql(docs);
              done();
            });

            cursorStream.pipe(stream);
          });
        });
      });
    });
  });

  describe('transforms', function () {
    it('should correctly apply map transform to cursor as readable stream', function (done) {
      const configuration = this.configuration;
      const client = configuration.newClient();
      client.connect(err => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const docs = 'Aaden Aaron Adrian Aditya Bob Joe'.split(' ').map(x => ({ name: x }));
        const coll = client.db(configuration.db).collection('cursor_stream_mapping');
        coll.insertMany(docs, err => {
          expect(err).to.not.exist;

          const bag = [];
          const stream = coll
            .find()
            .project({ _id: 0, name: 1 })
            .map(doc => ({ mapped: doc }))
            .stream()
            .on('data', doc => bag.push(doc));

          stream.on('error', done).on('end', () => {
            expect(bag.map(x => x.mapped)).to.eql(docs.map(x => ({ name: x.name })));
            done();
          });
        });
      });
    });

    it('should correctly apply map transform when converting cursor to array', function (done) {
      const configuration = this.configuration;
      const client = configuration.newClient();
      client.connect(err => {
        expect(err).to.not.exist;
        this.defer(() => client.close());

        const docs = 'Aaden Aaron Adrian Aditya Bob Joe'.split(' ').map(x => ({ name: x }));
        const coll = client.db(configuration.db).collection('cursor_toArray_mapping');
        coll.insertMany(docs, err => {
          expect(err).to.not.exist;

          coll
            .find()
            .project({ _id: 0, name: 1 })
            .map(doc => ({ mapped: doc }))
            .toArray((err, mappedDocs) => {
              expect(err).to.not.exist;
              expect(mappedDocs.map(x => x.mapped)).to.eql(docs.map(x => ({ name: x.name })));
              done();
            });
        });
      });
    });
  });

  context('sort', function () {
    const findSort = (input, output) =>
      function (done) {
        const client = this.configuration.newClient({ monitorCommands: true });
        const events = [];
        client.on('commandStarted', event => {
          if (event.commandName === 'find') {
            events.push(event);
          }
        });
        const db = client.db('test');
        const collection = db.collection('test_sort_dos');
        const cursor = collection.find({}, { sort: input });
        cursor.next(err => {
          expect(err).to.not.exist;
          expect(events[0].command.sort).to.be.instanceOf(Map);
          expect(Array.from(events[0].command.sort)).to.deep.equal(Array.from(output));
          client.close(done);
        });
      };

    const cursorSort = (input, output) =>
      function (done) {
        const client = this.configuration.newClient({ monitorCommands: true });
        const events = [];
        client.on('commandStarted', event => {
          if (event.commandName === 'find') {
            events.push(event);
          }
        });
        const db = client.db('test');
        const collection = db.collection('test_sort_dos');
        const cursor = collection.find({}).sort(input);
        cursor.next(err => {
          expect(err).to.not.exist;
          expect(events[0].command.sort).to.be.instanceOf(Map);
          expect(Array.from(events[0].command.sort)).to.deep.equal(Array.from(output));
          client.close(done);
        });
      };

    it('should use find options object', findSort({ alpha: 1 }, new Map([['alpha', 1]])));
    it('should use find options string', findSort('alpha', new Map([['alpha', 1]])));
    it('should use find options shallow array', findSort(['alpha', 1], new Map([['alpha', 1]])));
    it('should use find options deep array', findSort([['alpha', 1]], new Map([['alpha', 1]])));

    it('should use cursor.sort object', cursorSort({ alpha: 1 }, new Map([['alpha', 1]])));
    it('should use cursor.sort string', cursorSort('alpha', new Map([['alpha', 1]])));
    it('should use cursor.sort shallow array', cursorSort(['alpha', 1], new Map([['alpha', 1]])));
    it('should use cursor.sort deep array', cursorSort([['alpha', 1]], new Map([['alpha', 1]])));

    it('formatSort - one key', () => {
      // TODO (NODE-3236): These are unit tests for a standalone function and should be moved out of the cursor context file
      expect(formatSort('alpha')).to.deep.equal(new Map([['alpha', 1]]));
      expect(formatSort(['alpha'])).to.deep.equal(new Map([['alpha', 1]]));
      expect(formatSort('alpha', 1)).to.deep.equal(new Map([['alpha', 1]]));
      expect(formatSort('alpha', 'asc')).to.deep.equal(new Map([['alpha', 1]]));
      expect(formatSort([['alpha', 'asc']])).to.deep.equal(new Map([['alpha', 1]]));
      expect(formatSort('alpha', 'ascending')).to.deep.equal(new Map([['alpha', 1]]));
      expect(formatSort({ alpha: 1 })).to.deep.equal(new Map([['alpha', 1]]));
      expect(formatSort('beta')).to.deep.equal(new Map([['beta', 1]]));
      expect(formatSort(['beta'])).to.deep.equal(new Map([['beta', 1]]));
      expect(formatSort('beta', -1)).to.deep.equal(new Map([['beta', -1]]));
      expect(formatSort('beta', 'desc')).to.deep.equal(new Map([['beta', -1]]));
      expect(formatSort('beta', 'descending')).to.deep.equal(new Map([['beta', -1]]));
      expect(formatSort({ beta: -1 })).to.deep.equal(new Map([['beta', -1]]));
      expect(formatSort({ alpha: { $meta: 'hi' } })).to.deep.equal(
        new Map([['alpha', { $meta: 'hi' }]])
      );
    });

    it('formatSort - multi key', () => {
      expect(formatSort(['alpha', 'beta'])).to.deep.equal(
        new Map([
          ['alpha', 1],
          ['beta', 1]
        ])
      );
      expect(formatSort({ alpha: 1, beta: 1 })).to.deep.equal(
        new Map([
          ['alpha', 1],
          ['beta', 1]
        ])
      );
      expect(
        formatSort([
          ['alpha', 'asc'],
          ['beta', 'ascending']
        ])
      ).to.deep.equal(
        new Map([
          ['alpha', 1],
          ['beta', 1]
        ])
      );
      expect(
        formatSort(
          new Map([
            ['alpha', 'asc'],
            ['beta', 'ascending']
          ])
        )
      ).to.deep.equal(
        new Map([
          ['alpha', 1],
          ['beta', 1]
        ])
      );
      expect(
        formatSort([
          ['3', 'asc'],
          ['1', 'ascending']
        ])
      ).to.deep.equal(
        new Map([
          ['3', 1],
          ['1', 1]
        ])
      );
      expect(formatSort({ alpha: { $meta: 'hi' }, beta: 'ascending' })).to.deep.equal(
        new Map([
          ['alpha', { $meta: 'hi' }],
          ['beta', 1]
        ])
      );
    });

    it('should use allowDiskUse option on sort', {
      metadata: { requires: { mongodb: '>=4.4' } },
      test: async function () {
        const events = [];
        client.on('commandStarted', event => {
          if (event.commandName === 'find') {
            events.push(event);
          }
        });
        const db = client.db('test');
        const collection = db.collection('test_sort_allow_disk_use');
        const cursor = collection.find({}).sort(['alpha', 1]).allowDiskUse();
        await cursor.next();
        const { command } = events.shift();
        expect(command.sort).to.deep.equal(new Map([['alpha', 1]]));
        expect(command.allowDiskUse).to.be.true;
      }
    });

    it('should error if allowDiskUse option used without sort', {
      metadata: { requires: { mongodb: '>=4.4' } },
      test: async function () {
        const client = this.configuration.newClient();
        const db = client.db('test');
        const collection = db.collection('test_sort_allow_disk_use');
        expect(() => collection.find({}).allowDiskUse()).to.throw(
          /Option "allowDiskUse" requires a sort specification/
        );
        await client.close();
      }
    });
  });
});