New expectation functions plus convert old tests to use these.

lib/unittest/matcher.dart

+// Copyright (c) 2012, 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.
+
+/**
+ * Matcher is the base class for all matchers. To implement a new
+ * matcher, either add a class that implements from IMatcher or
+ * a class that inherits from Matcher. Inheriting from Matcher has
+ * the benefit that a default implementation of describeMismatch will
+ * be provided.
+ */
+
+class Matcher implements IMatcher {

[Bob Nystrom, 2012/05/30 23:23:51]

I would get rid of the separate interface and just keep this class. Most users
will subclass. If they don't want to inherit the implementation, they can always
implement the class's implicit interface.

[gram, 2012/06/01 17:33:15]

I'd rather not, if that's okay with you. Implementing the implicit interface is
a horrible kludge that presumably won't work in checked mode. Matcher is so
ubiquitous in this library I feel better using an interface.

[Bob Nystrom, 2012/06/01 18:22:22]

No, it works fine in checked mode. Implicit interfaces are a deep part of the
language. They exist in part so that you don't have to do the Java anti-pattern
of wrapping every class in an interface just in case you end up needing to
abstract it later. If there's only a single implementation, it's fine to just
start with a class.
If it makes you feel better, that's fine. Will both the class and interface be
exposed by the library? Can they subclass the class?

+
+  /**
+   * This tests the matcher against a given [item]
+   * and return true if the match succeeds; false otherwise.
+   */
+  bool matches(item) {

[Bob Nystrom, 2012/05/30 23:23:51]

Just make this abstract.

[gram, 2012/06/01 17:33:15]

Done.

+    throw new NotImplementedException(/*'matches'*/);
+  }
+
+  /**
+   * This creates a textual description of a matcher,
+   * by appending to [mismatchDescription].
+   */
+  IDescription describe(IDescription mismatchDescription) {

[Bob Nystrom, 2012/05/30 23:23:51]

This too.

[gram, 2012/06/01 17:33:15]

Done.

+    throw new NotImplementedException(/*'describe'*/);
+  }
+
+  /**
+   * This generates a description of the matcher failed for a particular

[Bob Nystrom, 2012/05/30 23:23:51]

"Generates a description of why the matcher failed..."

[gram, 2012/06/01 17:33:15]

Done.

+   * [item], by appending the description to [mismatchDescription].
+   * It does not check whether the [item] fails the match, as it is
+   * only called after a failed match.
+   */
+  IDescription describeMismatch(item, IDescription mismatchDescription) =>
+    mismatchDescription.append('was ').appendDescriptionOf(item);
+}
+