test(tests/commit.js): throw error if staging is empty

Extend upon the existing commit unit tests. Assert the error is thrown when running commitizen
commit command with no files add to staging.

"re commitizen#585"

test/tests/commit.js

@@ -311,6 +311,73 @@ ${(os.platform === 'win32') ? '' : '    '}
       done();
     });
   });
+
+  it('should throw error if staging area is empty', function (done) {
+
+    this.timeout(config.maxTimeout); // this could take a while
+
+    // SETUP
+
+    let dummyCommitMessage = `one does not simply ignore the tests`;
+
+    // Describe a repo and some files to add and commit
+    let repoConfig = {
+      path: config.paths.endUserRepo,
+      files: {
+        dummyfile: {
+          contents: `duck-duck-gray-duck`,
+          filename: `mydummiestfile.txt`,
+        },
+        gitignore: {
+          contents: `node_modules/`,
+          filename: `.gitignore`,
+        }
+      }
+    };
+
+    // Describe an adapter
+    let adapterConfig = {
+      path: path.join(repoConfig.path, '/node_modules/cz-jira-smart-commit'),
+      npmName: 'cz-jira-smart-commit'
+    };
+
+    // Quick setup the repos, adapter, and grab a simple prompter
+    let prompter = quickPrompterSetup(repoConfig, adapterConfig, dummyCommitMessage);
+    // TEST
+
+    // Make an initial commit
+    commitizenCommit(inquirer, repoConfig.path, prompter, { disableAppendPaths: true, quiet: true, emitData: true }, function (error) {
+      //  Should pass, as the files are added to the staging area
+      expect(error).to.be.null;
+
+      log(repoConfig.path, function (logOutput) {
+        expect(logOutput).to.have.string(dummyCommitMessage);
+      });
+      whatChanged(repoConfig.path, function (whatChangedOutput) {
+        expect(whatChangedOutput).to.have.string('A\t' + repoConfig.files.dummyfile.filename);
+
+        //  Make changes and don't add them to the staging area
+        writeFilesToPath({
+          dummymodified: {
+            contents: repoConfig.files.dummyfile.contents + '-modified',
+            filename: repoConfig.files.dummyfile.filename,
+            add: false,
+          }
+        }, repoConfig.path);
+        //  Define a dummy prompter
+        let prompter = function (cz, commit) {
+          commit(`${dummyCommitMessage} #2`, {});
+        };
+
+        commitizenCommit(inquirer, repoConfig.path, prompter, { disableAppendPaths: true, quiet: true, emitData: true }, function (error) {
+          //  Should fail, as staging are is empty
+          expect(error).to.be.instanceOf(Error);
+          done();
+        });
+      });
+    });
+
+  });
 });
 
 afterEach(function () {