Mocha adapter for Polymer browser tests.

chrome/test/data/webui/mocha_adapter.js

Index: chrome/test/data/webui/mocha_adapter.js
diff --git a/chrome/test/data/webui/mocha_adapter.js b/chrome/test/data/webui/mocha_adapter.js
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+// Copyright 2015 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 A mocha adapter for browser tests.
+ *
+ * Mocha requires a browser (or node), so mocha and this adapter should be
+ * included as part of the WebUI (i.e., as opposed to using GEN_INCLUDE).
+ */
+
+/**
+ * Initialize a reporter for the browser test framework.
+ * @param {Runner} runner
+ */
+function BrowserTestReporter(runner) {
+  var passes = 0;
+  var failures = 0;
+
+  // Increment passes for each passed test.
+  runner.on('pass', function(test) {
+    passes++;
+  });
+
+  // Report failures. Mocha only catches "assert" failures, because "expect"
+  // failures are caught by test_api.js.
+  runner.on('fail', function(test, err) {
+    failures++;
+    console.error('Test failed: ' + test.fullTitle());
+    // The error message given by test_api.js includes relevant details like
+    // actual and expected values. The stack trace of the error isn't useful.
+    console.error(err.message);
+  });
+
+  // Report the results to the browser test API.
+  runner.on('end', function() {
+    if (failures == 0)
+      testDone();
+    testDone([

[michaelpg, 2015/05/05 16:46:33]

should be "else {... }"

+        false,
+        'Test Errors: ' + failures + '/' + (passes + failures) + ' tests failed'
+    ]);
+  });
+}
+
+// Configure Mocha.
+mocha.setup({
+  // Use "tdd" interface instead of "bdd".
+  ui: 'tdd',
+  // Use custom reporter to interface with browser test.
+  reporter: BrowserTestReporter,
+});