New expectation functions plus convert old tests to use these.

lib/unittest/expect.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.
+
+/**
+ * This is the main assertion function. It asserts that [actual]
+ * matches the [matcher]. [reason] is optional and is typically
+ * not supplied, as a reason can be generated from the matcher.
+ * If [reason] is included it is appended to the reason generated
+ * by the matcher.
+ *
+ * If the assertion fails, then the default behavior is to throw an
+ * [ExpectException], but this behavior can be changed by calling
+ * [configureExpectHandler] and providing an alternative handler that
+ * implements the [IFailureHandler] interface.
+ *
+ * [expect] allows an alternative call format, providing a Boolean
+ * predicate as the first argument and an optional reason as the
+ * second argument. This supports brevity at the expense of detailed
+ * error messages. For example, these are equivalent, but the first
+ * form will give a detailed error message, while the second form will
+ * just give a generic assertion failed message:
+ *
+ *     expect(foo, isLessThanOrEqual(bar));
+ *     expect(foo <= bar);
+ *
+ * expect() is a 3rd generation assertion mechanism, drawing
+ * inspiration from [Hamcrest] and Ladislav Thon's [dart-matchers]
+ * library.
+ *
+ * See [Hamcrest] http://en.wikipedia.org/wiki/Hamcrest
+ *     [Hamcrest] http://http://code.google.com/p/hamcrest/
+ *     [dart-matchers] https://github.com/Ladicek/dart-matchers
+ */
+void expect(actual, [matcherOrReason = null, String reason = '']) {
+  if (matcherOrReason is Matcher) {
+    var doesMatch;
+    try {
+      doesMatch = matcherOrReason.matches(actual);
+    } catch (var e, var trace) {
+      doesMatch = false;
+      if (reason == '') {
+        reason = '${(e is String) ? e : e.toString()} at $trace';
+      }
+    }
+    if (!doesMatch) {
+      // Make sure we have a failure handler configured.
+      configureExpectHandler(_assertFailureHandler);
+      _assertFailureHandler.failMatch(actual, matcherOrReason, reason);
+    }
+  } else {
+    if (!actual) {
+      reason = (matcherOrReason == null) ? 'Assertion failed' : matcherOrReason;
+      // Make sure we have a failure handler configured.
+      configureExpectHandler(_assertFailureHandler);
+      _assertFailureHandler.fail(reason);
+    }
+  }
+}
+
+/**
+ * Takes an argument and returns an equivalent matcher.
+ * If the argument is already a matcher this does nothing, else it
+ * generates an equals matcher for the argument.
+ */
+Matcher wrapMatcher(x) => ((x is Matcher) ? x : equals(x));
+
+// The handler for failed asserts.
+FailureHandler _assertFailureHandler = null;
+
+// The default failure handler that throws ExpectExceptions.
+class DefaultFailureHandler implements FailureHandler {
+  DefaultFailureHandler() {
+    if (_assertErrorFormatter == null) {
+      _assertErrorFormatter = _defaultErrorFormatter;
+    }
+  }
+  void fail(String reason) {
+    throw new ExpectException(reason);
+  }
+  void failMatch(actual, Matcher matcher, String reason) {
+    fail(_assertErrorFormatter(actual, matcher, reason));
+  }
+}
+
+/**
+ * Changes or resets to the default the failure handler for expect()
+ * [handler] is a reference to the new handler; if this is omitted
+ * or null then the failure handler is reset to the default, which
+ * throws [ExpectExceptions] on [expect] assertion failures.
+ */
+void configureExpectHandler([FailureHandler handler = null]) {
+  if (handler == null) {
+    handler = new DefaultFailureHandler();
+  }
+  _assertFailureHandler = handler;
+}
+
+// The error message formatter for failed asserts.
+ErrorFormatter _assertErrorFormatter = null;
+
+// The default error formatter implementation.
+String _defaultErrorFormatter(actual, Matcher matcher, String reason) {
+  var description = new StringDescription();
+  description.add('Expected: ').addDescriptionOf(matcher).
+      add('\n     but: ');
+  matcher.describeMismatch(actual, description);
+  description.add('\n').add(reason).add('\n');
+  return description.toString();
+}
+
+/**
+ * Changes or resets to default the failure message formatter for expect().
+ * [formatter] is a reference to the new formatter; if this is omitted or
+ * null then the failure formatter is reset to the default. The new
+ * formatter is returned; this allows custom expect handlers to easily
+ * get a reference to the default formatter.
+ */
+ErrorFormatter configureExpectFormatter([ErrorFormatter formatter = null]) {
+  if (formatter == null) {
+    formatter = _defaultErrorFormatter;
+  }
+  return _assertErrorFormatter = formatter;
+}
+