add initial stats

connect stats

rename to collector

update documentation

signature update

add to reporter

hook back

fix test

remove space

test speed back into base

use single exports

handle correct cb in test

throw if missing runner, start event us event.once

updated documentation on module

updated docs and naming

Move typedef block above function docs block.

documentation update

move owner of stats to runner, from reporters

runner hands ref to reporter. Single export

mock runner needs stats

xunit tests need collector

cleanup xunit test. Single reporter var.

use typeError for stats

remove superfluous assignment

removed another unnecessary assignment

removed unnecessary return

lib/reporters/base.js

@@ -271,9 +271,7 @@ exports.list = function(failures) {
  * Initialize a new `Base` reporter.
  *
  * All other reporters generally
- * inherit from this reporter, providing
- * stats such as test duration, number
- * of tests passed / failed etc.
+ * inherit from this reporter.
  *
  * @memberof Mocha.reporters
  * @public
@@ -283,68 +281,31 @@ exports.list = function(failures) {
  */
 
 function Base(runner) {
-  var stats = (this.stats = {
-    suites: 0,
-    tests: 0,
-    passes: 0,
-    pending: 0,
-    failures: 0
-  });
   var failures = (this.failures = []);
 
   if (!runner) {
-    return;
+    throw new TypeError('Missing runner argument');
   }
+  this.stats = runner.stats; // attached so Reporters have a reference
   this.runner = runner;
 
-  runner.stats = stats;
-
-  runner.on('start', function() {
-    stats.start = new Date();
-  });
-
-  runner.on('suite', function(suite) {
-    stats.suites = stats.suites || 0;
-    suite.root || stats.suites++;
-  });
-
-  runner.on('test end', function() {
-    stats.tests = stats.tests || 0;
-    stats.tests++;
-  });
-
   runner.on('pass', function(test) {
-    stats.passes = stats.passes || 0;
-
     if (test.duration > test.slow()) {
       test.speed = 'slow';
     } else if (test.duration > test.slow() / 2) {
       test.speed = 'medium';
     } else {
       test.speed = 'fast';
     }
-
-    stats.passes++;
   });
 
   runner.on('fail', function(test, err) {
-    stats.failures = stats.failures || 0;
-    stats.failures++;
     if (showDiff(err)) {
       stringifyDiffObjs(err);
     }
     test.err = err;
     failures.push(test);
   });
-
-  runner.once('end', function() {
-    stats.end = new Date();
-    stats.duration = stats.end - stats.start;
-  });
-
-  runner.on('pending', function() {
-    stats.pending++;
-  });
 }
 
 /**

lib/runner.js

@@ -12,6 +12,7 @@ var utils = require('./utils');
 var inherits = utils.inherits;
 var debug = require('debug')('mocha:runner');
 var Runnable = require('./runnable');
+var createStatsCollector = require('./stats-collector');
 var stackFilter = utils.stackTraceFilter();
 var stringify = utils.stringify;
 var type = utils.type;
@@ -81,6 +82,7 @@ function Runner(suite, delay) {
   this._defaultGrep = /.*/;
   this.grep(this._defaultGrep);
   this.globals(this.globalProps().concat(extraGlobals()));
+  createStatsCollector(this);
 }
 
 /**

lib/stats-collector.js

@@ -0,0 +1,70 @@
+'use strict';
+
+/**
+ * Test statistics collector.
+ *
+ * @typedef {Object} StatsCollector
+ * @property {number} suites - integer count of suites run.
+ * @property {number} tests - integer count of tests run.
+ * @property {number} passes - integer count of passing tests.
+ * @property {number} pending - integer count of pending tests.
+ * @property {number} failures - integer count of failed tests.
+ * @property {Date} start - time when testing began.
+ * @property {Date} end - time when testing concluded.
+ * @property {number} duration - number of msecs that testing took.
+ */
+
+/**
+ * Provides stats such as test duration,
+ * number of tests passed / failed etc.
+ *
+ * @public
+ * @memberof Mocha
+ * @param {Runner} runner
+ */
+function createStatsCollector(runner) {
+  var stats = {
+    suites: 0,
+    tests: 0,
+    passes: 0,
+    pending: 0,
+    failures: 0
+  };
+
+  if (!runner) {
+    throw new TypeError('Missing runner argument');
+  }
+
+  runner.stats = stats;
+
+  runner.once('start', function() {
+    stats.start = new Date();
+  });
+
+  runner.on('suite', function(suite) {
+    suite.root || stats.suites++;
+  });
+
+  runner.on('pass', function() {
+    stats.passes++;
+  });
+
+  runner.on('fail', function() {
+    stats.failures++;
+  });
+
+  runner.on('pending', function() {
+    stats.pending++;
+  });
+
+  runner.on('test end', function() {
+    stats.tests++;
+  });
+
+  runner.once('end', function() {
+    stats.end = new Date();
+    stats.duration = stats.end - stats.start;
+  });
+}
+
+module.exports = createStatsCollector;

test/reporters/helpers.js

@@ -8,6 +8,8 @@
   scope of this function for the tests to run properly.
 */
 
+var createStatsCollector = require('../../lib/stats-collector');
+
 function createMockRunner(runStr, ifStr1, ifStr2, ifStr3, arg1, arg2) {
   var runnerFunction = createRunnerFunction(
     runStr,
@@ -17,10 +19,12 @@ function createMockRunner(runStr, ifStr1, ifStr2, ifStr3, arg1, arg2) {
     arg1,
     arg2
   );
-  return {
+  var mockRunner = {
     on: runnerFunction,
     once: runnerFunction
   };
+  createStatsCollector(mockRunner);
+  return mockRunner;
 }
 
 function createRunnerFunction(runStr, ifStr1, ifStr2, ifStr3, arg1, arg2) {

test/reporters/list.spec.js

@@ -21,6 +21,7 @@ describe('List reporter', function() {
     duration: expectedDuration,
     slow: function() {}
   };
+
   beforeEach(function() {
     useColors = Base.useColors;
     Base.useColors = false;
@@ -126,7 +127,11 @@ describe('List reporter', function() {
       test = {};
       runner = createMockRunner('fail', 'fail', null, null, test);
       runner.on = runner.once = function(event, callback) {
-        if (!checked && event === 'fail') {
+        if (
+          !checked &&
+          event === 'fail' &&
+          callback.toString().includes('stringifyDiffObjs') // target correct fail event callback
+        ) {
           err = new Error('fake failure object with actual/expected');
           err.actual = actual;
           err.expected = expected;

test/reporters/xunit.spec.js

@@ -4,12 +4,14 @@ var fs = require('fs');
 var mkdirp = require('mkdirp');
 var path = require('path');
 var assert = require('assert');
+var createStatsCollector = require('../../lib/stats-collector');
 var reporters = require('../../').reporters;
 var XUnit = reporters.XUnit;
 
 describe('XUnit reporter', function() {
   var stdout;
   var stdoutWrite;
+  // the runner parameter of the reporter
   var runner;
 
   var callbackArgument = null;
@@ -26,6 +28,7 @@ describe('XUnit reporter', function() {
   beforeEach(function() {
     stdout = [];
     runner = {on: function() {}, once: function() {}};
+    createStatsCollector(runner);
   });
 
   describe('if reporter options output is given', function() {
@@ -322,8 +325,6 @@ describe('XUnit reporter', function() {
   describe('custom suite name', function() {
     // capture the events that the reporter subscribes to
     var events;
-    // the runner parameter of the reporter
-    var runner;
     // capture output lines (will contain the resulting XML of the xunit reporter)
     var lines;
     // the file stream into which the xunit reporter will write into
@@ -332,13 +333,10 @@ describe('XUnit reporter', function() {
     beforeEach(function() {
       events = {};
 
-      runner = {
-        on: function(eventName, eventHandler) {
-          // capture the event handler
-          events[eventName] = eventHandler;
-        }
+      runner.on = runner.once = function(eventName, eventHandler) {
+        // capture the event handler
+        events[eventName] = eventHandler;
       };
-      runner.once = runner.on;
 
       lines = [];
       fileStream = {