Add an accessibility audit test for WebUI pages

chrome/test/data/webui/accessibility_audit_browsertest.js

+// Copyright (c) 2012 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 Tests to ensure that the accessibility audit and mechanisms
+ * to enable/disable it work as expected.
+ * @author aboxhall@google.com (Alice Boxhall)
+ * @see test_api.js
+ */
+
+/**
+ * Test fixture for accessibility audit test.
+ * @constructor
+ * @extends testing.Test
+ */
+function WebUIAccessibilityAuditBrowserTest() {}
+
+WebUIAccessibilityAuditBrowserTest.prototype = {
+  __proto__: testing.Test.prototype,
+
+  browsePreload: 'chrome://terms',
+
+  runAccessibilityChecks: true,
+  accessibilityIssuesAreErrors: true,
+
+  /**
+   * Number of expected accessibility errors, if it should be checked, otherwise
+   * null. Note: 'a11y' is short for 'accessibility'
+   * @type {?number}
+   */
+  expectedWarnings: null,
+
+  /**
+   * Number of expected accessibility warnings, if it should be checked,
+   * otherwise null.
+   * @type {?number}
+   */
+  expectedErrors: null,
+
+  tearDown: function() {
+    if (this.expectedErrors != null)
+      expectEquals(this.expectedErrors, getAccessibilityErrors().length);
+    if (this.expectedWarnings != null)
+      expectEquals(this.expectedWarnings, getAccessibilityWarnings().length);
+    testing.Test.prototype.tearDown.call(this);
+  }
+};
+
+/**
+ * Adds some canned audit failures to the page being tested:
+ * - A low-contrast (white on white) element
+ * - An element with a non-existent ARIA role
+ * - A control without a label
+ */
+function addAuditFailures() {
+  // Contrast ratio
+  var style = document.createElement('style');
+  style.innerText = 'p { color: #ffffff }';
+  document.head.appendChild(style);
+
+  // Bad ARIA role
+  var div = document.createElement('div');
+  div.setAttribute('role', 'not-a-role');
+  document.body.appendChild(div);
+
+  // Unlabelled control
+  var input = document.createElement('input');
+  input.type = 'text';
+  document.body.appendChild(input);
+}
+
+/**
+ * Adds an expectation that console.warn() will be called at least once with
+ * a string matching '.*accessibility.*'.
+ */
+function expectReportConsoleWarning() {
+  function StubConsole() {};
+  StubConsole.prototype.warn = function() {};
+  StubConsole.prototype.log = function() {};
+  StubConsole.prototype.error = function() {};
+  var mockConsole = mock(StubConsole);
+  mockConsole.expects(atLeastOnce()).warn(stringContains('accessibility'));
+  mockConsole.stubs().log(ANYTHING);
+  mockConsole.stubs().error(ANYTHING);
+  console = mockConsole.proxy();
+}
+
+/**
+ * Creates a mock axs.Audit object.
+ * @return {object} a mock object with a run() method.
+ */
+function createMockAudit() {
+  function StubAudit() {};
+  StubAudit.prototype.run = function() {};
+  return mock(StubAudit);
+}
+
+/**
+ * Creates an expectation that the global axs.Audit object will never have its
+ * run() method called.
+ */
+function expectAuditWillNotRun() {
+  var audit = createMockAudit();
+  audit.expects(never()).run();
+  axs.Audit = audit.proxy();
+}
+
+/**
+ * Creates an expectation that the global axs.Audit object will have its run()
+ * method called |times| times.
+ * This creates an interstitial mock axs.Audit object with the expectation, and
+ * delegates to the real axs.Audit object to run the actual audit.
+ * @param {number} times The number of times the audit is expected to run.
+ */
+function expectAuditWillRun(times) {
+  var audit = createMockAudit();
+  var realAudit = axs.Audit;
+  var expectedInvocation = audit.expects(exactly(times)).run();
+  var willArgs = [];
+  for (var i = 0; i < times; i++)
+    willArgs.push(callFunction(realAudit.run));
+  expectedInvocation.will.apply(expectedInvocation, willArgs);
+  axs.Audit = audit.proxy();
+}
+
+// Test that an audit failure causes a test failure, if both
+// |runAccessibilityChecks| and |accessibilityIssuesAreErrors| are true.
+TEST_F('WebUIAccessibilityAuditBrowserTest', 'testWithAuditFailures_shouldFail',
+       function() {
+  expectAuditWillRun(1);
+  addAuditFailures();
+});
+
+// Test that the accessibility audit does not run if |runAccessibilityChecks|
+// is false.
+TEST_F('WebUIAccessibilityAuditBrowserTest',
+       'testWithAuditFailures_a11yChecksDisabled',
+       function() {
+  expectAuditWillNotRun();
+  disableAccessibilityChecks();
+  addAuditFailures();
+});
+
+// Tests that the accessibility audit will run but not cause a test failure when
+// accessibilityIssuesAreErrors(false) is called in the test function
+TEST_F('WebUIAccessibilityAuditBrowserTest',
+       'testWithAuditFailures_a11yIssuesAreWarnings',
+        function() {
+  accessibilityIssuesAreErrors(false);
+  expectAuditWillRun(1);
+  expectReportConsoleWarning();
+
+  this.expectedWarnings = 1;
+  this.expectedErrors = 2;
+  enableAccessibilityChecks();
+  addAuditFailures();
+});
+
+/**
+ * Test fixture with |runAccessibilityChecks| set to false.
+ * @constructor
+ * @extends {WebUIAccessibilityAuditBrowserTest}
+ */
+function WebUIAccessibilityAuditBrowserTest_TestsDisabledInFixture() {}
+
+WebUIAccessibilityAuditBrowserTest_TestsDisabledInFixture.prototype = {
+  __proto__: WebUIAccessibilityAuditBrowserTest.prototype,
+
+  runAccessibilityChecks: false,
+  accessibilityIssuesAreErrors: true,
+};
+
+// Test that the accessibility audit does not run when |runAccessibilityChecks|
+// is set to false in the test fixture.
+TEST_F('WebUIAccessibilityAuditBrowserTest_TestsDisabledInFixture',
+       'testWithAuditFailures_a11yChecksNotEnabled',
+       function() {
+  expectAuditWillNotRun();
+  addAuditFailures();
+});
+
+// Test that the accessibility audit does run if the enableAccessibilityChecks()
+// method is called in the test function.
+TEST_F('WebUIAccessibilityAuditBrowserTest_TestsDisabledInFixture',
+       'testWithAuditFailures_shouldFail',
+       function() {
+  expectAuditWillRun(1);
+  enableAccessibilityChecks();
+  addAuditFailures();
+});
+
+// Test that the accessibility audit runs when the expectAccessibilityOk()
+// method is called.
+TEST_F('WebUIAccessibilityAuditBrowserTest_TestsDisabledInFixture',
+       'testRunningAuditManually_noErrors',
+       function() {
+  expectAuditWillRun(1);
+  expectAccessibilityOk();
+});
+
+// Test that calling expectAccessibilityOk() when there are accessibility issues
+// on the page causes the test to fail.
+TEST_F('WebUIAccessibilityAuditBrowserTest_TestsDisabledInFixture',
+       'testRunningAuditManually_withErrors_shouldFail',
+       function() {
+  expectAuditWillRun(1);
+  addAuditFailures();
+  expectAccessibilityOk();
+});
+
+// Test that calling expectAccessibilityOk() multiple times will cause the
+// accessibility audit to run multiple times.
+TEST_F('WebUIAccessibilityAuditBrowserTest_TestsDisabledInFixture',
+       'testRunningAuditManuallySeveralTimes', function() {
+  expectAuditWillRun(2);
+  expectAccessibilityOk();
+  expectAccessibilityOk();
+});
+
+/**
+ * Test fixture with |accessibilityIssuesAreErrors| set to false.
+ * @constructor
+ * @extends {WebUIAccessibilityAuditBrowserTest}
+ */
+function WebUIAccessibilityAuditBrowserTest_IssuesAreWarnings() {}
+
+WebUIAccessibilityAuditBrowserTest_IssuesAreWarnings.prototype = {
+  __proto__: WebUIAccessibilityAuditBrowserTest.prototype,
+
+  accessibilityIssuesAreErrors: false,
+};
+
+// Tests that the accessibility audit will run but not cause a test failure when
+// |accessibilityIssuesAreErrors| is false in the test fixture.
+TEST_F('WebUIAccessibilityAuditBrowserTest_IssuesAreWarnings',
+       'testWithAuditFailures',
+        function() {
+  expectAuditWillRun(1);
+  expectReportConsoleWarning();
+  this.expectedWarnings = 1;
+  this.expectedErrors = 2;
+
+  enableAccessibilityChecks();
+  addAuditFailures();
+});
+
+// Tests that the accessibility audit will run and call a test failure when
+// accessibilityIssuesAreErrors(true) is called in the test function.
+TEST_F('WebUIAccessibilityAuditBrowserTest_IssuesAreWarnings',
+       'testWithAuditFailuresAndIssuesAreErrors_shouldFail',
+        function() {
+  expectAuditWillRun(1);
+  this.expectedWarnings = 1;
+  this.expectedErrors = 2;
+
+  accessibilityIssuesAreErrors(true)
+  enableAccessibilityChecks();
+
+  addAuditFailures();
+});
+
+// Tests that the accessibility audit will run twice if expectAccessibilityOk()
+// is called during the test function and |runAccessibilityChecks| is true in
+// the test fixture.
+TEST_F('WebUIAccessibilityAuditBrowserTest_IssuesAreWarnings',
+       'testWithAuditFailuresAndExpectA11yOk',
+        function() {
+  expectAuditWillRun(2);
+
+  expectAccessibilityOk();
+
+  this.expectedWarnings = 1;
+  this.expectedErrors = 2;
+  expectReportConsoleWarning();
+
+  enableAccessibilityChecks();
+
+  addAuditFailures();
+});