When we have excess callbacks, throw instead of calling error() so that we

pkg/unittest/lib/src/config.dart

Index: pkg/unittest/lib/src/config.dart
===================================================================
--- pkg/unittest/lib/src/config.dart	(revision 19267)
+++ pkg/unittest/lib/src/config.dart	(working copy)
@@ -15,10 +15,7 @@
   // The VM won't shut down if a receive port is open. Use this to make sure
   // we correctly wait for asynchronous tests.
   ReceivePort _receivePort;
-  TestCase _currentTestCase;
 
-  TestCase get currentTestCase => _currentTestCase;
-
   /**
    * Subclasses can override this with something useful for diagnostics.
    * Particularly useful in cases where we have parent/child configurations
@@ -53,32 +50,34 @@
    */
   void onTestStart(TestCase testCase) {
     assert(testCase != null);	
-    assert(_currentTestCase == null);
-    _currentTestCase = testCase;
   }
 
   /**
-   * Called when each test is completed. Useful to show intermediate progress on
-   * a test suite.
+   * Called when each test is first completed. Useful to show intermediate
+   * progress on a test suite.
    */
   void onTestResult(TestCase testCase) {
     assert(testCase != null);	
-    assert(_currentTestCase == null || _currentTestCase == testCase);
-    _currentTestCase = null;
   }
 
   /**
+   * Called when an already completed test changes state; for example a test
+   * that was marked as passing may later be marked as being in error because
+   * it still had callbacks being invoked.
+   */
+  void onTestResultChanged(TestCase testCase) {
+    assert(testCase != null);
+  }
+
+  /**
    * Can be called by tests to log status. Tests should use this
    * instead of print. Subclasses should not override this; they
    * should instead override logMessage which is passed the test case.
    */
   void logMessage(String message) {
-    if (currentTestCase == null || _currentTest >= _tests.length ||
-        currentTestCase.id != _tests[_currentTest].id) {
-      // Before or after tests run, or with a mismatch between what the
-      // config and the test harness think is the current test. In this
-      // case we pass null for the test case reference and let the config
-      // decide what to do with this.
+    if (currentTestCase == null) {
+      // Before or after tests run. In this case we pass null for the test
+      // case reference and let the config decide what to do with this.
       logTestCaseMessage(null, message);
     } else {
       logTestCaseMessage(currentTestCase, message);