pkg/(unit)test: include a copy of old matcher

lib/src/matcher/map_matchers.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.
+
+library matcher.map_matchers;
+
+import 'interfaces.dart';
+import 'util.dart';
+
+/// Returns a matcher which matches maps containing the given [value].
+Matcher containsValue(value) => new _ContainsValue(value);
+
+class _ContainsValue extends Matcher {
+  final _value;
+
+  const _ContainsValue(this._value);
+
+  bool matches(item, Map matchState) => item.containsValue(_value);
+  Description describe(Description description) =>
+      description.add('contains value ').addDescriptionOf(_value);
+}
+
+/// Returns a matcher which matches maps containing the key-value pair
+/// with [key] => [value].
+Matcher containsPair(key, value) =>
+    new _ContainsMapping(key, wrapMatcher(value));
+
+class _ContainsMapping extends Matcher {
+  final _key;
+  final Matcher _valueMatcher;
+
+  const _ContainsMapping(this._key, Matcher this._valueMatcher);
+
+  bool matches(item, Map matchState) =>
+      item.containsKey(_key) && _valueMatcher.matches(item[_key], matchState);
+
+  Description describe(Description description) {
+    return description
+        .add('contains pair ')
+        .addDescriptionOf(_key)
+        .add(' => ')
+        .addDescriptionOf(_valueMatcher);
+  }
+
+  Description describeMismatch(
+      item, Description mismatchDescription, Map matchState, bool verbose) {
+    if (!item.containsKey(_key)) {
+      return mismatchDescription
+          .add(" doesn't contain key ")
+          .addDescriptionOf(_key);
+    } else {
+      mismatchDescription
+          .add(' contains key ')
+          .addDescriptionOf(_key)
+          .add(' but with value ');
+      _valueMatcher.describeMismatch(
+          item[_key], mismatchDescription, matchState, verbose);
+      return mismatchDescription;
+    }
+  }
+}