step 1 in making unittest platform independent.

lib/unittest/config.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.
+
+/** Signature for the [Configuration.onTestResult] callback. */
+typedef void ResultCallback(TestCase testCase);
+
+/** Signature for the [Configuration.onDone] callback. */
+typedef void DoneCallback(
+    int passed, int failed, int errors, List<TestCase> results);
+
+/** Hooks to configure the unittest library for different platforms. */
+class Configuration {

[Bob Nystrom, 2012/04/10 00:30:31]

A class full of functions is a bit strange. How about just making those
functions methods (and make their implementations be the _defaultConfig() stuff
below). Then the other implementations can subclass it and override the methods
they care about.

[Siggi Cherem (dart-lang), 2012/04/10 01:05:28]

Good point - this was a bit historical (I used to make this configuration one
that you could override by setting a particular listener programatically).

Done.

+  /**
+   * Called as soon as the unittest framework becomes initialized. This is done
+   * even before tests are added to the test framework. It might be used to
+   * determine/debug errors that occur before the test harness starts executing.
+   */
+  final Function onInit;
+
+  /**
+   * Called as soon as the unittest framework starts running. Used commonly to
+   * tell the vm or browser that tests are still running and the process should
+   * wait until they are done.
+   */
+  final Function onStart;
+
+  /**
+   * Called when each test is completed. The default implementation
+   * throws an exception if the test failed. Other implementations might choose to
+   * ignore this callback and present a summary result in [onDone].
+   */
+  final ResultCallback onTestResult;
+
+  /**
+   * Called with the result of all test cases. The default implementation prints
+   * the result summary using the built-in [print] command. Browser tests
+   * commonly override this to reformat the output.
+   */
+  final DoneCallback onDone;
+
+  Configuration(this.onInit, this.onStart, this.onTestResult, this.onDone);
+}
+
+// TODO(sigmund): make this the default config.
+//Configuration _defaultConfig() {
+//  final onInit = () {};
+//  final onStart = () {};
+//  final onResult = (TestCase testCase) { 
+//    if (testCase.result != _PASS) {
+//      Expect.fail("FAIL: ${testCase.description}");
+//    }
+//  };
+//  final onDone = (int passed, int failed, int errors, List<TestCase> results) {
+//    if (failed == 0 && errors == 0) {
+//      print("PASS");
+//    }
+//  };
+//  return new Configuration(onInit, onStart, onResult, onDone);
+//}