New WebAudio layout testing utility: audit.js

third_party/WebKit/LayoutTests/webaudio/resources/audit.js

Index: third_party/WebKit/LayoutTests/webaudio/resources/audit.js
diff --git a/third_party/WebKit/LayoutTests/webaudio/resources/audit.js b/third_party/WebKit/LayoutTests/webaudio/resources/audit.js
new file mode 100644
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+++ b/third_party/WebKit/LayoutTests/webaudio/resources/audit.js
@@ -0,0 +1,980 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+
+/**
+ * @fileOverview  WebAudio layout test utility library. Built around W3C's
+ *                testharness.js. Includes asynchronous test task manager,
+ *                assertion utilities.
+ * @dependency    testharness.js
+ * @seealso       webaudio/unit-tests/audit.html for actual examples.
+ */
+
+
+(function () {
+
+  'use strict';
+
+  // Selected properties from testharness.js
+  let testharnessProperties = [
+    'test', 'async_test', 'promise_test', 'promise_rejects',
+    'generate_tests', 'setup', 'done', 'assert_true', 'assert_false'
+  ];
+
+  // Check if testharness.js is properly loaded. Throw otherwise.
+  for (let name in testharnessProperties) {
+    if (!self.hasOwnProperty(testharnessProperties[name])) {
+      throw new Error('Cannot proceed. testharness.js is not loaded.');
+      break;
+    }
+  }
+})();
+
+
+/**
+ * @class Audit
+ * @description A WebAudio layout test task manager.
+ * @example
+ *   let audit = Audit.createTaskRunner();
+ *   audit.define('first-task', function (task, should) {
+ *     task.describe('the first task');
+ *     should(someValue).beEqualTo(someValue);
+ *     task.done();
+ *   });
+ *   audit.run();
+ */
+window.Audit = (function () {
+
+  'use strict';
+
+  function _logPassed (message) {
+    test(function (arg) {
+      assert_true(true);
+    }, message);
+  }
+
+  function _logFailed (message, detail) {
+    test(function () {
+      assert_true(false, detail);
+    }, message);
+  }
+
+  function _throwException (message) {
+    throw new Error(message);
+  }
+
+  // Generate a descriptive string from a target value in various types.
+  function _generateDescription (target, options) {
+    let targetString;
+
+    switch (typeof target) {
+      case 'object':
+        // Handle Arrays.
+        if (target instanceof Array || target instanceof Float32Array ||
+            target instanceof Float64Array) {
+          let arrayElements = target.length < options.numberOfArrayElements
+              ? String(target)
+              : String(target.slice(0, options.numberOfArrayElements)) + '...';
+          targetString = '[' + arrayElements + ']';
+        } else {
+          targetString = '' + String(targetString).split(/[\s\]]/)[1];
+        }
+        break;
+      default:
+        targetString = String(target);
+        break;
+    }
+
+    return targetString;
+  }
+
+
+  /**
+   * @class Should
+   * @description Assertion subtask for the Audit task.
+   * @param {Task} parentTask           Associated Task object.
+   * @param {Any} actual                Target value to be tested.
+   * @param {String} actualDescription  String description of the test target.
+   */
+  class Should {
+
+    constructor (parentTask, actual, actualDescription) {
+      this._task = parentTask;
+
+      this._actual = actual;
+      this._actualDescription = (actualDescription || null);
+      this._expected = null;
+      this._expectedDescription = null;
+
+      this._result = true;
+      this._detail = '';
+
+      /**
+       * @param {Number} numberOfErrors   Number of errors to be printed.
+       * @param {Number} numberOfArrayElements  Number of array elements to be
+       *                                        printed in the test log.
+       * @param {Boolean} verbose         Verbose output from the assertion.
+       */
+      this._options = {
+        numberOfErrors: 4,
+        numberOfArrayElements: 16,
+        verbose: false
+      };
+    }
+
+    _processArguments (args) {
+      if (args.length === 0)
+        return;
+
+      if (args.length > 0)
+        this._expected = args[0];
+
+      if (typeof args[1] === 'string') {
+        // case 1: (expected, description, options)
+        this._expectedDescription = args[1];
+        Object.assign(this._options, args[2]);
+      } else if (typeof args[1] === 'object') {
+        // case 2: (expected, options)
+        Object.assign(this._options, args[1]);
+      }
+    }
+
+    _buildResultText () {
+      if (!this._actualDescription) {
+        this._actualDescription =
+            _generateDescription(this._actual, this._options);
+      }
+
+      if (!this._expectedDescription) {
+        this._expectedDescription =
+            _generateDescription(this._expected, this._options);
+      }
+
+      // For the assertion with a single operand.
+      this._detail = this._detail.replace('${actual}', this._actualDescription);
+
+      // If there is a second operand (i.e. expected value), we have to build
+      // the string for it as well.
+      if (this._expected) {
+        this._detail = this._detail.replace(
+            '${expected}', this._expectedDescription);
+      }
+
+      // If there is any property in |_options|, replace the property name
+      // with the value.
+      for (let name in this._options) {
+        this._detail = this._detail.replace(
+            '${' + name + '}',
+            _generateDescription(this._options[name]));
+      }
+    }
+
+    _finalize () {
+      if (this._result) {
+        _logPassed('  ' + this._detail);
+      } else {
+        _logFailed('X ' + this._detail);
+      }
+
+      // This assertion is finished, so update the parent task accordingly.
+      this._task.update(this);
+
+      // TODO(hongchan): configurable 'detail' message.
+    }
+
+    _assert (condition, passDetail, failDetail) {
+      this._result = Boolean(condition);
+      this._detail = this._result ? passDetail : failDetail;
+      this._buildResultText();
+      return this._finalize();
+    }
+
+    get result () {
+      return this._result;
+    }
+
+    get detail () {
+      return this._detail;
+    }
+
+    /**
+     * should() assertions.
+     *
+     * @example All the assertions can have 1, 2 or 3 arguments:
+     *   should().doAssert(expected);
+     *   should().doAssert(expected, options);
+     *   should().doAssert(expected, expectedDescription, options);
+     *
+     * @param {Any} expected                  Expected value of the assertion.
+     * @param {String} expectedDescription    Description of expected value.
+     * @param {Object} options                Options for assertion.
+     * @param {Number} options.numberOfErrors Number of errors to be printed.
+     *                                        (if applicable)
+     * @param {Number} options.numberOfArrayElements  Number of array elements
+     *                                                to be printed. (if
+     *                                                applicable)
+     * @notes Some assertions can have additional options for their specific
+     *        testing.
+     */
+
+    /**
+     * Check if |actual| exists.
+     *
+     * @example
+     *   should({}, 'An empty object').exist();
+     * @result
+     *   "PASS   An empty object does exist."
+     */
+    exist () {
+      return this._assert(
+          this._actual !== null && this._actual !== undefined,
+          '${actual} does exist.',
+          '${actual} does *NOT* exist.');
+    }
+
+    /**
+     * Check if |actual| operation wrapped in a function throws an exception
+     * with a expected error type correctly. |expected| is optional.
+     *
+     * @example
+     *   should(() => { let a = b; }, 'A bad code').throw();
+     *   should(() => { let c = d; }, 'Assigning d to c.')
+     *       .throw('ReferenceError');
+     *
+     * @result
+     *   "PASS   A bad code threw an exception of ReferenceError."
+     *   "PASS   Assigning d to c threw ReferenceError."
+     */
+    throw () {
+      this._processArguments(arguments);
+
+      let didThrowCorrectly = false;
+      let passDetail, failDetail;
+
+      try {
+        // This should throw.
+        this._actual();
+        // Catch did not happen, so the test is failed.
+        failDetail = '${actual} did *NOT* throw an exception.';
+      } catch (error) {
+        if (this._expected === undefined) {
+          didThrowCorrectly = true;
+          passDetail = '${actual} threw an exception of ' + error.name + '.';
+        } else if (error.name === this._expected) {
+          didThrowCorrectly = true;
+          passDetail = '${actual} threw ${expected} : "' + error.message + '".';
+        } else {
+          didThrowCorrectly = false;
+          failDetail = '${actual} threw "' + error.name
+            + '" instead of ${expected}.';
+        }
+      }
+
+      return this._assert(didThrowCorrectly, passDetail, failDetail);
+    }
+
+    /**
+     * Check if |actual| operation wrapped in a function does not throws an
+     * exception correctly.
+     *
+     * @example
+     *   should(() => { let foo = 'bar'; }, 'let foo = "bar"').notThrow();
+     *
+     * @result
+     *   "PASS   let foo = "bar" did not throw an exception."
+     */
+    notThrow () {
+      let didThrowCorrectly = false;
+      let passDetail, failDetail;
+
+      try {
+        this._actual();
+        passDetail = '${actual} did not throw an exception.';
+      } catch (error) {
+        didThrowCorrectly = true;
+        failDetail = '${actual} threw ' + error.name + ': '
+            + error.message + '.';
+      }
+
+      return this._assert(!didThrowCorrectly, passDetail, failDetail);
+    }
+
+    /**
+     * Check if |actual| promise is resolved correctly.
+     *
+     * @example
+     *   should('My promise', promise).beResolve().then(nextStuff);
+     *
+     * @result
+     *   "PASS   My promise resolved correctly."
+     *   "FAIL X My promise rejected *INCORRECTLY* with _ERROR_."
+     */
+    beResolved () {
+      return this._actual.then(function () {
+          this._assert(true, '${actual} resolved correctly.', null);
+        }.bind(this), function (error) {
+          this._assert(false, null,
+              '${actual} rejected *INCORRECTLY* with ' + error + '.');
+        }.bind(this));
+    }
+
+    /**
+     * Check if |actual| promise is rejected correctly.
+     *
+     * @example
+     *   should('My promise', promise).beRejected().then(nextStuff);
+     *
+     * @result
+     *   "PASS   My promise rejected correctly (with _ERROR_)."
+     *   "FAIL X My promise resolved *INCORRECTLY*."
+     */
+    beRejected () {
+      return this._actual.then(function () {
+          this._assert(false, null, '${actual} resolved *INCORRECTLY*.');
+        }.bind(this), function (error) {
+          this._assert(true,
+              '${actual} rejected correctly with ' + error + '.', null);
+        }.bind(this));
+    }
+
+    /**
+     * Check if |actual| is a boolean true.
+     *
+     * @example
+     *   should(3 < 5, '3 < 5').beTrue();
+     *
+     * @result
+     *   "PASS   3 < 5 is true."
+     */
+    beTrue () {
+      return this._assert(
+          this._actual === true,
+          '${actual} is true.',
+          '${actual} is *NOT* true.');
+    }
+
+    /**
+     * Check if |actual| is a boolean false.
+     *
+     * @example
+     *   should(3 > 5, '3 > 5').beFalse();
+     *
+     * @result
+     *   "PASS   3 > 5 is false."
+     */
+    beFalse () {
+      return this._assert(
+          this._actual === false,
+          '${actual} is false.',
+          '${actual} is *NOT* false.');
+    }
+
+    /**
+     * Check if |actual| is strictly equal to |expected|. (no type coercion)
+     *
+     * @example
+     *   should(1).beEqualTo(1);
+     *
+     * @result
+     *   "PASS   1 is equal to 1."
+     */
+    beEqualTo () {
+      this._processArguments(arguments);
+      return this._assert(
+          this._actual === this._expected,
+          '${actual} is equal to ${expected}.',
+          '${actual} is *NOT* equal to ${expected}.');
+    }
+
+    /**
+     * Check if |actual| is not equal to |expected|.
+     *
+     * @example
+     *   should(1).notBeEqualTo(2);
+     *
+     * @result
+     *   "PASS   1 is *NOT* equal to 2."
+     */
+    notBeEqualTo () {
+      this._processArguments(arguments);
+      return this._assert(
+          this._actual !== this._expected,
+          '${actual} is not equal to ${expected}.',
+          '${actual} should *NOT* be equal to ${expected}.');
+    }
+
+    /**
+     * Check if |actual| is greater than |expected|.
+     *
+     * @example
+     *   should(2).beGreaterThanOrEqualTo(2);
+     *
+     * @result
+     *   "PASS   2 is greater than or equal to 2."
+     */
+    beGreaterThan () {
+      this._processArguments(arguments);
+      return this._assert(
+          this._actual > this._expected,
+           '${actual} is greater than ${expected}.',
+           '${actual} is *NOT* greater than ${expected}.'
+        );
+    }
+
+    /**
+     * Check if |actual| is greater than or equal to |expected|.
+     *
+     * @example
+     *   should(2).beGreaterThan(1);
+     *
+     * @result
+     *   "PASS   2 is greater than 1."
+     */
+    beGreaterThanOrEqualTo () {
+      this._processArguments(arguments);
+      return this._assert(
+          this._actual >= this._expected,
+           '${actual} is greater than or equal to ${expected}.',
+           '${actual} is *NOT* greater than or equal to ${expected}.'
+        );
+    }
+
+    /**
+     * Check if |actual| is less than |expected|.
+     *
+     * @example
+     *   should(1).beLessThan(2);
+     *
+     * @result
+     *   "PASS   1 is less than 2."
+     */
+    beLessThan () {
+      this._processArguments(arguments);
+      return this._assert(
+          this._actual < this._expected,
+           '${actual} is less than ${expected}.',
+           '${actual} is *NOT* less than ${expected}.'
+        );
+    }
+
+    /**
+     * Check if |actual| is less than or equal to |expected|.
+     *
+     * @example
+     *   should(1).beLessThanOrEqualTo(1);
+     *
+     * @result
+     *   "PASS   1 is less than or equal to 1."
+     */
+    beLessThanOrEqualTo () {
+      this._processArguments(arguments);
+      return this._assert(
+          this._actual <= this._expected,
+           '${actual} is less than or equal to ${expected}.',
+           '${actual} is *NOT* less than or equal to ${expected}.'
+        );
+    }
+
+    /**
+     * Check if |actual| array is filled with a constant |expected| value.
+     *
+     * @example
+     *   should([1, 1, 1]).beConstantValueOf(1);
+     *
+     * @result
+     *   "PASS   [1,1,1] contains only the constant 1."
+     */
+    beConstantValueOf () {
+      this._processArguments(arguments);
+
+      let passed = true;
+      let passDetail, failDetail;
+      let errors = {};
+
+      for (let index in this._actual) {
+        if (this._actual[index] !== this._expected)
+          errors[index] = this._actual[index];
+      }
+
+      let numberOfErrors = Object.keys(errors).length;
+      passed = numberOfErrors === 0;
+
+      if (passed) {
+        passDetail = '${actual} contains only the constant ${expected}.';
+      } else {
+        let counter = 0;
+        failDetail = '${actual} contains ' + numberOfErrors
+          + ' values that are *NOT* equal to ${expected}: ';
+        failDetail += '\n\tIndex\tActual';
+        for (let errorIndex in errors) {
+          failDetail += '\n\t[' + errorIndex + ']'
+              + '\t' + errors[errorIndex];
+          if (++counter >= this._options.numberOfErrors) {
+            failDetail += '\n\t...and ' + (numberOfErrors - counter)
+              + ' more errors.';
+            break;
+          }
+        }
+      }
+
+      return this._assert(passed, passDetail, failDetail);
+    }
+
+    /**
+     * Check if |actual| array is identical to |expected| array element-wise.
+     *
+     * @example
+     *   should([1, 2, 3]).beEqualToArray([1, 2, 3]);
+     *
+     * @result
+     *   "[1,2,3] is identical to the array [1,2,3]."
+     */
+    beEqualToArray () {
+      this._processArguments(arguments);
+
+      let passed = true;
+      let passDetail, failDetail;
+      let errorIndices = [];
+
+      if (this._actual.length !== this._expected.length) {
+        passed = false;
+        failDetail = 'The array length does *NOT* match.';
+        return this._assert(passed, passDetail, failDetail);
+      }
+
+      for (let index in this._actual) {
+        if (this._actual[index] !== this._expected[index])
+          errorIndices.push(index);
+      }
+
+      passed = errorIndices.length === 0;
+
+      if (passed) {
+        passDetail = '${actual} is identical to the array ${expected}.';
+      } else {
+        let counter = 0;
+        failDetail = '${actual} contains ' + errorIndices.length
+          + ' values that are *NOT* equal to ${expected}: ';
+        failDetail += '\n\tIndex\tActual\t\t\tExpected';
+        for (let index of errorIndices) {
+          failDetail += '\n\t[' + index + ']'
+            + '\t' + this._actual[index].toExponential(16)
+            + '\t' + this._expected[index].toExponential(16);
+          if (++counter >= this._options.numberOfErrors) {
+            failDetail += '\n\t...and ' + (numberOfErrors - counter)
+              + ' more errors.';
+            break;
+          }
+        }
+      }
+
+      return this._assert(passed, passDetail, failDetail);
+    }
+
+    /**
+     * Check if |actual| array contains only the values in |expected| in the
+     * order of values in |expected|.
+     *
+     * @example
+     *   Should([1, 1, 3, 3, 2], 'My random array').containValues([1, 3, 2]);
+     *
+     * @result
+     *   "PASS   [1,1,3,3,2] contains all the expected values in the correct
+     *           order: [1,3,2].
+     */
+    containValues () {
+      this._processArguments(arguments);
+
+      let passed = true;
+      let indexActual = 0, indexExpected = 0;
+
+      while (indexActual < this._actual.length
+          && indexExpected < this._expected.length) {
+        if (this._actual[indexActual] === this._expected[indexExpected]) {
+          indexActual++;
+        } else {
+          indexExpected++;
+        }
+      }
+
+      passed = !(indexActual < this._actual.length - 1
+          || indexExpected < this._expected.length - 1);
+
+      return this._assert(
+          passed,
+          '${actual} contains all the expected values in the correct order: '
+            + '${expected}.',
+          '${actual} contains an unexpected value of '
+            + this._actual[indexActual] + ' at index ' + indexActual + '.');
+    }
+
+    /**
+     * Check if |actual| array does not have any glitches. Note that |threshold|
+     * is not optional and is to define the desired threshold value.
+     *
+     * @example
+     *   should([0.5, 0.5, 0.55, 0.5, 0.45, 0.5]).notGlitch(0.06);
+     *
+     * @result
+     *   "PASS   [0.5,0.5,0.55,0.5,0.45,0.5] has no glitch above the threshold
+     *           of 0.06."
+     *
+     */
+    notGlitch () {
+      this._processArguments(arguments);
+
+      let passed = true;
+      let passDetail, failDetail;
+
+      for (let index in this._actual) {
+        let diff = Math.abs(this._actual[index - 1] - this._actual[index]);
+        if (diff >= this._expected) {
+          passed = false;
+          failDetail = '${actual} has a glitch at index ' + index + ' of size '
+            + diff + '.';
+        }
+      }
+
+      passDetail =
+        '${actual} has no glitch above the threshold of ${expected}.';
+
+      return this._assert(passed, passDetail, failDetail);
+    }
+
+    /**
+     * Check if |actual| is close to |expected| using the given relative error
+     * |threshold|.
+     *
+     * @example
+     *   should(2.3).beCloseTo(2, 0.3);
+     *
+     * @result
+     *   "PASS    2.3 is 2 within an error of 0.3."
+     *
+     * @param {Number} options.threshold    Threshold value for the comparison.
+     */
+    beCloseTo () {
+      this._processArguments(arguments);
+
+      let absExpected = this._expected ? Math.abs(this._expected) : 1;
+      let error = Math.abs(this._actual - this._expected) / absExpected;
+
+      return this._assert(
+        error < this._options.threshold,
+        '${actual} is ${expected} within an error of ${threshold}',
+        '${actual} is not ${expected} within a error of ${threshold}: ' +
+          '${actual} with error of ${threshold}.');
+    }
+
+    /**
+     * Check if |target| array is close to |expected| array element-wise within
+     * a certain error bound given by the |options|.
+     *
+     * The error criterion is:
+     *   abs(actual[k] - expected[k]) < max(absErr, relErr * abs(expected))
+     *
+     * If nothing is given for |options|, then absErr = relErr = 0. If
+     * absErr = 0, then the error criterion is a relative error. A non-zero
+     * absErr value produces a mix intended to handle the case where the
+     * expected value is 0, allowing the target value to differ by absErr from
+     * the expected.
+     *
+     * @param {Number} options.absoluteThreshold    Absolute threshold.
+     * @param {Number} options.relativeThreshold    Relative threshold.
+     */
+    beCloseToArray () {
+      this._processArguments(arguments);
+
+      let passed = true;
+      let passDetail, failDetail;
+
+      // Parsing options.
+      let absErrorThreshold = (this._options.absoluteThreshold || 0);
+      let relErrorThreshold = (this._options.relativeThreshold || 0);
+
+      // A collection of all of the values that satisfy the error criterion.
+      // This holds the absolute difference between the target element and the
+      // expected element.
+      let errors = {};
+
+      // Keep track of the max absolute error found.
+      let maxAbsError = -Infinity, maxAbsErrorIndex = -1;
+
+      // Keep track of the max relative error found, ignoring cases where the
+      // relative error is Infinity because the expected value is 0.
+      let maxRelError = -Infinity, maxRelErrorIndex = -1;
+
+      for (let index in this._expected) {
+        let diff = Math.abs(this._actual[index] - this._expected[index]);
+        let absExpected = Math.abs(this._expected[index]);
+        let relError = diff / absExpected;
+
+        if (diff > Math.max(absErrorThreshold,
+                            relErrorThreshold * absExpected)) {
+
+          if (diff > maxAbsError) {
+            maxAbsErrorIndex = index;
+            maxAbsError = diff;
+          }
+
+          if (!isNaN(relError) && relError > maxRelError) {
+            maxRelErrorIndex = index;
+            maxRelError = relError;
+          }
+
+          errors[index] = diff;
+        }
+      }
+
+      let numberOfErrors = Object.keys(errors).length;
+      let maxAllowedErrorDetail = JSON.stringify({
+        absoluteThreshold: absErrorThreshold,
+        relativeThreshold: relErrorThreshold
+      });
+
+      if (numberOfErrors === 0) {
+        // The assertion was successful.
+        passDetail = '${actual} equals ${expected} with an element-wise '
+          + 'tolerance of ' + maxAllowedErrorDetail + '.';
+      } else {
+        // Failed. Prepare the detailed failure log.
+        passed = false;
+        failDetail = '${actual} does not equal ${expected} with an '
+          + 'element-wise tolerance of ' + maxAllowedErrorDetail + '.\n';
+
+        // Print out actual, expected, absolute error, and relative error.
+        let counter = 0;
+        failDetail += '\tIndex\tActual\t\t\tExpected\t\tAbsError'
+            + '\t\tRelError\t\tTest threshold';
+        for (let index in errors) {
+          failDetail += '\n\t[' + index + ']\t'
+              + this._actual[index].toExponential(16) + '\t'
+              + this._expected[index].toExponential(16) + '\t'
+              + errors[index].toExponential(16) + '\t'
+              + (errors[index] / Math.abs(this._expected[index]))
+                  .toExponential(16) + '\t'
+              + Math.max(absErrorThreshold,
+                    relErrorThreshold * Math.abs(this._expected[index]))
+                      .toExponential(16);
+          if (++counter > this._options.numberOfErrors)
+            break;
+        }
+
+        // Finalize the error log: print out the location of both the maxAbs
+        // error and the maxRel error so we can adjust thresholds appropriately
+        // in the test.
+        failDetail += '\n'
+            + '\tMax AbsError of ' + maxAbsError.toExponential(16)
+            + ' at index of ' + maxAbsErrorIndex + '.\n'
+            + '\tMax RelError of ' + maxRelError.toExponential(16)
+            + ' at index of ' + maxRelErrorIndex + '.';
+      }
+
+      return this._assert(passed, passDetail, failDetail);
+    }
+
+  }
+
+
+  // Task Class state enum.
+  const TaskState = {
+    PENDING: 0,
+    STARTED: 1,
+    FINISHED: 2
+  };
+
+
+  /**
+   * @class Task
+   * @description WebAudio testing task. Managed by TaskRunner.
+   */
+  class Task {
+
+    constructor (taskRunner, taskLabel, taskFunction) {
+      this._taskRunner = taskRunner;
+      this._taskFunction = taskFunction;
+      this._label = taskLabel;
+      this._description = '';
+      this._state = TaskState.PENDING;
+      this._result = true;
+
+      this._totalAssertions = 0;
+      this._failedAssertions = 0;
+    }
+
+    // Set the description of this task. This is printed out in the test
+    // result.
+    describe (message) {
+      this._description = message;
+      _logPassed('> [' + this._label + '] '
+          + this._description);
+    }
+
+    get state () {
+      return this._state;
+    }
+
+    get result () {
+      return this._result;
+    }
+
+    // Start the assertion chain.
+    should (actual, actualDescription) {
+      return new Should(this, actual, actualDescription);
+    }
+
+    // Run this task. |this| task will be passed into the user-supplied test
+    // task function.
+    run () {
+      this._state = TaskState.STARTED;
+      this._taskFunction(
+          this,
+          this.should.bind(this));
+    }
+
+    // Update the task success based on the individual assertion/test inside.
+    update (subTask) {
+      // After one of tests fails within a task, the result is irreversible.
+      if (subTask.result === false) {
+        this._result = false;
+        this._failedAssertions++;
+      }
+
+      this._totalAssertions++;
+    }
+
+    // Finish the current task and start the next one if available.
+    done () {
+      this._state = TaskState.FINISHED;
+
+      let message = '< [' + this._label + '] ';
+
+      if (this._result) {
+        message += 'All assertion passed. (total ' + this._totalAssertions
+          + ' assertions)';
+        _logPassed(message);
+      } else {
+        message += this._failedAssertions + ' out of ' + this._totalAssertions
+          + ' assertions were failed.'
+        _logFailed(message);
+      }
+
+      this._taskRunner._runNextTask();
+    }
+
+    isPassed () {
+      return this._state === TaskState.FINISHED && this._result;
+    }
+
+    toString () {
+      return '"' + this._label + '": ' + this._description;
+    }
+
+  }
+
+
+  /**
+   * @class TaskRunner
+   * @description WebAudio testing task runner. Manages tasks.
+   */
+  class TaskRunner {
+
+    constructor () {
+      this._tasks = {};
+      this._taskSequence = [];
+      this._currentTaskIndex = -1;
+
+      // Configure testharness.js for the async operation.
+      setup (new Function (), {
+        explicit_done: true
+      });
+    }
+
+    _runNextTask () {
+      if (this._currentTaskIndex < this._taskSequence.length) {
+        this._tasks[this._taskSequence[this._currentTaskIndex++]].run();
+      } else {
+        this._finish();
+      }
+    }
+
+    _finish () {
+      let numberOfFailures = 0;
+      for (let taskIndex in this._taskSequence) {
+        let task = this._tasks[this._taskSequence[taskIndex]];
+        numberOfFailures += task.result ? 0 : 1;
+      }
+
+      let prefix = '# AUDIT TASK RUNNER FINISHED: ';
+      if (numberOfFailures > 0) {
+        _logFailed(prefix + numberOfFailures + ' out of '
+          + this._taskSequence.length + ' tasks were failed.');
+      } else {
+        _logPassed(prefix + this._taskSequence.length
+          + ' tasks ran successfully.');
+      }
+
+      // From testharness.js, report back to the test infrastructure that
+      // the task runner completed all the tasks.
+      done();
+    }
+
+    define (taskLabel, taskFunction) {
+      if (this._tasks.hasOwnProperty(taskLabel)) {
+        _throwException('Audit.define:: Duplicate task definition.');
+        return;
+      }
+
+      this._tasks[taskLabel] = new Task(this, taskLabel, taskFunction);
+      this._taskSequence.push(taskLabel);
+    }
+
+    // Start running all the tasks scheduled. Multiple task names can be passed
+    // to execute them sequentially. Zero argument will perform all defined
+    // tasks in the order of definition.
+    run () {
+      // Display the beginning of the test suite.
+      _logPassed('# AUDIT TASK RUNNER STARTED.');
+
+      // If the argument is specified, override the default task sequence with
+      // the specified one.
+      if (arguments.length > 0) {
+        this._taskSequence = [];
+        for (let i = 0; arguments.length; i++) {
+          let taskLabel = arguments[i];
+          if (!this._tasks.hasOwnProperty(taskLabel)) {
+            _throwException('Audit.run:: undefined task.');
+          } else if (this._taskSequence.includes(taskLabel)) {
+            _throwException('Audit.run:: duplicate task request.');
+          } else {
+            this._taskSequence.push[taskLabel];
+          }
+        }
+      }
+
+      if (this._taskSequence.length === 0) {
+        _throwException('Audit.run:: no task to run.');
+        return;
+      }
+
+      // Start the first task.
+      this._currentTaskIndex = 0;
+      this._runNextTask();
+    }
+
+  }
+
+
+  return {
+
+    /**
+     * Creates an instance of Audit task runner.
+     */
+    createTaskRunner: function () {
+      return new TaskRunner();
+    }
+
+  };
+
+})();