Extract runReporter to capture output under tests (mochajs#3528)

While refactoring the `dot` reporter test, we created a method for capturing output from running the reporter. It proved so handy at squelching test "noise" that JeongHoon extracted it and applied it to many of the other reporters.
TwineHealth · Nov 5, 2018 · 8a6a4e2 · 8a6a4e2
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diff --git a/test/reporters/doc.spec.js b/test/reporters/doc.spec.js
@@ -4,22 +4,15 @@ var reporters = require('../../').reporters;
 var Doc = reporters.Doc;
 
 var createMockRunner = require('./helpers.js').createMockRunner;
+var makeRunReporter = require('./helpers.js').createRunReporterFunction;
 
 describe('Doc reporter', function() {
-  var stdout;
-  var stdoutWrite;
   var runner;
-  beforeEach(function() {
-    stdout = [];
-    stdoutWrite = process.stdout.write;
-    process.stdout.write = function(string, enc, callback) {
-      stdout.push(string);
-      stdoutWrite.call(process.stdout, string, enc, callback);
-    };
-  });
+  var options = {};
+  var runReporter = makeRunReporter(Doc);
 
   afterEach(function() {
-    process.stdout.write = stdoutWrite;
+    runner = undefined;
   });
 
   describe('on suite', function() {
@@ -32,8 +25,7 @@ describe('Doc reporter', function() {
       };
       it('should log html with indents and expected title', function() {
         runner = createMockRunner('suite', 'suite', null, null, suite);
-        Doc.call(this, runner);
-        process.stdout.write = stdoutWrite;
+        var stdout = runReporter(this, runner, options);
         var expectedArray = [
           '    <section class="suite">\n',
           '      <h1>' + expectedTitle + '</h1>\n',
@@ -48,8 +40,7 @@ describe('Doc reporter', function() {
         };
         expectedTitle = '&#x3C;div&#x3E;' + expectedTitle + '&#x3C;/div&#x3E;';
         runner = createMockRunner('suite', 'suite', null, null, suite);
-        Doc.call(this, runner);
-        process.stdout.write = stdoutWrite;
+        var stdout = runReporter(this, runner, options);
         var expectedArray = [
           '    <section class="suite">\n',
           '      <h1>' + expectedTitle + '</h1>\n',
@@ -64,8 +55,7 @@ describe('Doc reporter', function() {
       };
       it('should not log any html', function() {
         runner = createMockRunner('suite', 'suite', null, null, suite);
-        Doc.call(this, runner);
-        process.stdout.write = stdoutWrite;
+        var stdout = runReporter(this, runner, options);
         expect(stdout, 'to be empty');
       });
     });
@@ -78,8 +68,7 @@ describe('Doc reporter', function() {
       };
       it('should log expected html with indents', function() {
         runner = createMockRunner('suite end', 'suite end', null, null, suite);
-        Doc.call(this, runner);
-        process.stdout.write = stdoutWrite;
+        var stdout = runReporter(this, runner, options);
         var expectedArray = ['  </dl>\n', '</section>\n'];
         expect(stdout, 'to equal', expectedArray);
       });
@@ -90,8 +79,7 @@ describe('Doc reporter', function() {
       };
       it('should not log any html', function() {
         runner = createMockRunner('suite end', 'suite end', null, null, suite);
-        Doc.call(this, runner);
-        process.stdout.write = stdoutWrite;
+        var stdout = runReporter(this, runner, options);
         expect(stdout, 'to be empty');
       });
     });
@@ -109,8 +97,7 @@ describe('Doc reporter', function() {
     };
     it('should log html with indents and expected title and body', function() {
       runner = createMockRunner('pass', 'pass', null, null, test);
-      Doc.call(this, runner);
-      process.stdout.write = stdoutWrite;
+      var stdout = runReporter(this, runner, options);
       var expectedArray = [
         '    <dt>' + expectedTitle + '</dt>\n',
         '    <dd><pre><code>' + expectedBody + '</code></pre></dd>\n'
@@ -128,8 +115,7 @@ describe('Doc reporter', function() {
       var expectedEscapedBody =
         '&#x3C;div&#x3E;' + expectedBody + '&#x3C;/div&#x3E;';
       runner = createMockRunner('pass', 'pass', null, null, test);
-      Doc.call(this, runner);
-      process.stdout.write = stdoutWrite;
+      var stdout = runReporter(this, runner, options);
       var expectedArray = [
         '    <dt>' + expectedEscapedTitle + '</dt>\n',
         '    <dd><pre><code>' + expectedEscapedBody + '</code></pre></dd>\n'
@@ -158,8 +144,7 @@ describe('Doc reporter', function() {
         test,
         expectedError
       );
-      Doc.call(this, runner);
-      process.stdout.write = stdoutWrite;
+      var stdout = runReporter(this, runner, options);
       var expectedArray = [
         '    <dt class="error">' + expectedTitle + '</dt>\n',
         '    <dd class="error"><pre><code>' +
@@ -190,8 +175,7 @@ describe('Doc reporter', function() {
         test,
         unescapedError
       );
-      Doc.call(this, runner);
-      process.stdout.write = stdoutWrite;
+      var stdout = runReporter(this, runner, options);
       var expectedArray = [
         '    <dt class="error">' + expectedEscapedTitle + '</dt>\n',
         '    <dd class="error"><pre><code>' +

diff --git a/test/reporters/dot.spec.js b/test/reporters/dot.spec.js
@@ -5,42 +5,17 @@ var Dot = reporters.Dot;
 var Base = reporters.Base;
 
 var createMockRunner = require('./helpers.js').createMockRunner;
+var makeRunReporter = require('./helpers.js').createRunReporterFunction;
 
 describe('Dot reporter', function() {
-  var stdout;
   var runner;
   var useColors;
   var windowWidth;
   var color;
-  var showOutput = false;
-
-  /**
-   * Run reporter using stream reassignment to capture output.
-   *
-   * @param {Object} stubSelf - Reporter-like stub instance
-   * @param {Runner} runner - Mock instance
-   * @param {boolean} [tee=false] - If `true`, echo captured output to screen
-   */
-  function runReporter(stubSelf, runner, tee) {
-    // Reassign stream in order to make a copy of all reporter output
-    var stdoutWrite = process.stdout.write;
-    process.stdout.write = function(string, enc, callback) {
-      stdout.push(string);
-      if (tee) {
-        stdoutWrite.call(process.stdout, string, enc, callback);
-      }
-    };
-
-    // Invoke reporter
-    Dot.call(stubSelf, runner);
-
-    // Revert stream reassignment here so reporter output
-    // can't be corrupted if any test assertions throw
-    process.stdout.write = stdoutWrite;
-  }
+  var options = {};
+  var runReporter = makeRunReporter(Dot);
 
   beforeEach(function() {
-    stdout = [];
     useColors = Base.useColors;
     windowWidth = Base.window.width;
     color = Base.color;
@@ -61,7 +36,7 @@ describe('Dot reporter', function() {
   describe('on start', function() {
     it('should write a newline', function() {
       runner = createMockRunner('start', 'start');
-      runReporter({epilogue: function() {}}, runner, showOutput);
+      var stdout = runReporter({epilogue: function() {}}, runner, options);
       var expectedArray = ['\n'];
       expect(stdout, 'to equal', expectedArray);
     });
@@ -73,15 +48,15 @@ describe('Dot reporter', function() {
       });
       it('should write a newline followed by a comma', function() {
         runner = createMockRunner('pending', 'pending');
-        runReporter({epilogue: function() {}}, runner, showOutput);
+        var stdout = runReporter({epilogue: function() {}}, runner, options);
         var expectedArray = ['\n  ', 'pending_' + Base.symbols.comma];
         expect(stdout, 'to equal', expectedArray);
       });
     });
     describe('if window width is equal to or less than 1', function() {
       it('should write a comma', function() {
         runner = createMockRunner('pending', 'pending');
-        runReporter({epilogue: function() {}}, runner, showOutput);
+        var stdout = runReporter({epilogue: function() {}}, runner, options);
         var expectedArray = ['pending_' + Base.symbols.comma];
         expect(stdout, 'to equal', expectedArray);
       });
@@ -101,7 +76,7 @@ describe('Dot reporter', function() {
       describe('if test speed is fast', function() {
         it('should write a newline followed by a dot', function() {
           runner = createMockRunner('pass', 'pass', null, null, test);
-          runReporter({epilogue: function() {}}, runner, showOutput);
+          var stdout = runReporter({epilogue: function() {}}, runner, options);
           expect(test.speed, 'to equal', 'fast');
           var expectedArray = ['\n  ', 'fast_' + Base.symbols.dot];
           expect(stdout, 'to equal', expectedArray);
@@ -112,7 +87,7 @@ describe('Dot reporter', function() {
       describe('if test speed is fast', function() {
         it('should write a grey dot', function() {
           runner = createMockRunner('pass', 'pass', null, null, test);
-          runReporter({epilogue: function() {}}, runner, showOutput);
+          var stdout = runReporter({epilogue: function() {}}, runner, options);
           expect(test.speed, 'to equal', 'fast');
           var expectedArray = ['fast_' + Base.symbols.dot];
           expect(stdout, 'to equal', expectedArray);
@@ -122,7 +97,7 @@ describe('Dot reporter', function() {
         it('should write a yellow dot', function() {
           test.duration = 2;
           runner = createMockRunner('pass', 'pass', null, null, test);
-          runReporter({epilogue: function() {}}, runner, showOutput);
+          var stdout = runReporter({epilogue: function() {}}, runner, options);
           expect(test.speed, 'to equal', 'medium');
           var expectedArray = ['medium_' + Base.symbols.dot];
           expect(stdout, 'to equal', expectedArray);
@@ -132,7 +107,7 @@ describe('Dot reporter', function() {
         it('should write a bright yellow dot', function() {
           test.duration = 3;
           runner = createMockRunner('pass', 'pass', null, null, test);
-          runReporter({epilogue: function() {}}, runner, showOutput);
+          var stdout = runReporter({epilogue: function() {}}, runner, options);
           expect(test.speed, 'to equal', 'slow');
           var expectedArray = ['bright-yellow_' + Base.symbols.dot];
           expect(stdout, 'to equal', expectedArray);
@@ -152,15 +127,15 @@ describe('Dot reporter', function() {
       });
       it('should write a newline followed by an exclamation mark', function() {
         runner = createMockRunner('fail', 'fail', null, null, test);
-        runReporter({epilogue: function() {}}, runner, showOutput);
+        var stdout = runReporter({epilogue: function() {}}, runner, options);
         var expectedArray = ['\n  ', 'fail_' + Base.symbols.bang];
         expect(stdout, 'to equal', expectedArray);
       });
     });
     describe('if window width is equal to or less than 1', function() {
       it('should write an exclamation mark', function() {
         runner = createMockRunner('fail', 'fail', null, null, test);
-        runReporter({epilogue: function() {}}, runner, showOutput);
+        var stdout = runReporter({epilogue: function() {}}, runner, options);
         var expectedArray = ['fail_' + Base.symbols.bang];
         expect(stdout, 'to equal', expectedArray);
       });
@@ -173,7 +148,7 @@ describe('Dot reporter', function() {
       var epilogue = function() {
         epilogueCalled = true;
       };
-      runReporter({epilogue: epilogue}, runner, showOutput);
+      runReporter({epilogue: epilogue}, runner, options);
       expect(epilogueCalled, 'to be', true);
     });
   });

diff --git a/test/reporters/helpers.js b/test/reporters/helpers.js
@@ -155,9 +155,51 @@ function makeExpectedTest(
   };
 }
 
+/**
+ * Creates closure with reference to the reporter class constructor.
+ *
+ * @param {Function} ctor - Reporter class constructor
+ * @return {createRunReporterFunction~runReporter}
+ */
+function createRunReporterFunction(ctor) {
+  /**
+   * Run reporter using stream reassignment to capture output.
+   *
+   * @param {Object} stubSelf - Reporter-like stub instance
+   * @param {Runner} runner - Mock instance
+   * @param {Object} [options] - Reporter configuration settings
+   * @param {boolean} [tee=false] - Whether to echo output to screen
+   * @return {string[]} Lines of output written to `stdout`
+   */
+  var runReporter = function(stubSelf, runner, options, tee) {
+    var stdout = [];
+
+    // Reassign stream in order to make a copy of all reporter output
+    var stdoutWrite = process.stdout.write;
+    process.stdout.write = function(string, enc, callback) {
+      stdout.push(string);
+      if (tee) {
+        stdoutWrite.call(process.stdout, string, enc, callback);
+      }
+    };
+
+    // Invoke reporter
+    ctor.call(stubSelf, runner, options);
+
+    // Revert stream reassignment here so reporter output
+    // can't be corrupted if any test assertions throw
+    process.stdout.write = stdoutWrite;
+
+    return stdout;
+  };
+
+  return runReporter;
+}
+
 module.exports = {
-  createMockRunner: createMockRunner,
-  makeTest: makeTest,
   createElements: createElements,
-  makeExpectedTest: makeExpectedTest
+  createMockRunner: createMockRunner,
+  createRunReporterFunction: createRunReporterFunction,
+  makeExpectedTest: makeExpectedTest,
+  makeTest: makeTest
 };
diff --git a/test/reporters/json-stream.spec.js b/test/reporters/json-stream.spec.js
@@ -5,12 +5,12 @@ var JSONStream = reporters.JSONStream;
 
 var createMockRunner = require('./helpers').createMockRunner;
 var makeExpectedTest = require('./helpers').makeExpectedTest;
+var makeRunReporter = require('./helpers.js').createRunReporterFunction;
 
-describe('Json Stream reporter', function() {
+describe('JSON Stream reporter', function() {
   var runner;
-  var stdout;
-  var stdoutWrite;
-
+  var options = {};
+  var runReporter = makeRunReporter(JSONStream);
   var expectedTitle = 'some title';
   var expectedFullTitle = 'full title';
   var expectedDuration = 1000;
@@ -27,27 +27,16 @@ describe('Json Stream reporter', function() {
     message: expectedErrorMessage
   };
 
-  beforeEach(function() {
-    stdout = [];
-    stdoutWrite = process.stdout.write;
-    process.stdout.write = function(string, enc, callback) {
-      stdout.push(string);
-      stdoutWrite.call(process.stdout, string, enc, callback);
-    };
-  });
-
   afterEach(function() {
-    process.stdout.write = stdoutWrite;
+    runner = undefined;
   });
 
   describe('on start', function() {
     it('should write stringified start with expected total', function() {
       runner = createMockRunner('start', 'start');
       var expectedTotal = 12;
       runner.total = expectedTotal;
-      JSONStream.call({}, runner);
-
-      process.stdout.write = stdoutWrite;
+      var stdout = runReporter({}, runner, options);
 
       expect(
         stdout[0],
@@ -60,9 +49,7 @@ describe('Json Stream reporter', function() {
   describe('on pass', function() {
     it('should write stringified test data', function() {
       runner = createMockRunner('pass', 'pass', null, null, expectedTest);
-      JSONStream.call({}, runner);
-
-      process.stdout.write = stdoutWrite;
+      var stdout = runReporter({}, runner, options);
 
       expect(
         stdout[0],
@@ -93,9 +80,7 @@ describe('Json Stream reporter', function() {
           expectedError
         );
 
-        JSONStream.call({}, runner);
-
-        process.stdout.write = stdoutWrite;
+        var stdout = runReporter({}, runner, options);
 
         expect(
           stdout[0],
@@ -129,8 +114,7 @@ describe('Json Stream reporter', function() {
           expectedError
         );
 
-        JSONStream.call({}, runner);
-        process.stdout.write = stdoutWrite;
+        var stdout = runReporter(this, runner, options);
 
         expect(
           stdout[0],
@@ -154,8 +138,7 @@ describe('Json Stream reporter', function() {
   describe('on end', function() {
     it('should write end details', function() {
       runner = createMockRunner('end', 'end');
-      JSONStream.call({}, runner);
-      process.stdout.write = stdoutWrite;
+      var stdout = runReporter(this, runner, options);
       expect(stdout[0], 'to match', /end/);
     });
   });