pkg/unittest: Moved `fail` to matcher library

pkg/unittest/lib/unittest.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * A library for writing dart unit tests.
  *
  * To import this library, use the pub package manager.
  * Create a pubspec.yaml file in your project and add
  * a dependency on unittest with the following lines:
@@ skipping 810 matching lines @@
   _config.onDone(passed > 0 && failed == 0 && errors == 0 &&
       _uncaughtErrorMessage == null);
   _initialized = false;
 }
 
 String _fullSpec(String spec) {
   if (spec == null) return '$_currentGroup';
   return _currentGroup != '' ? '$_currentGroup$groupSep$spec' : spec;
 }
 
-void fail(String message) {
-  throw new TestFailure(message);
-}
-
 /**
  * Lazily initializes the test library if not already initialized.
  */
 ensureInitialized() {
   if (_initialized) {
     return;
   }
   _initialized = true;
   // Hook our async guard into the matcher library.
   wrapAsync = expectAsync1;
@@ skipping 40 matching lines @@
 }
 
 /** Enable a test by ID. */
 void enableTest(int testId) => _setTestEnabledState(testId, true);
 
 /** Disable a test by ID. */
 void disableTest(int testId) => _setTestEnabledState(testId, false);
 
 /** Signature for a test function. */
 typedef dynamic TestFunction();