pkg/unittest: readonly view of testCase collection

pkg/unittest/test/unittest_test.dart

Index: pkg/unittest/test/unittest_test.dart
diff --git a/pkg/unittest/test/unittest_test.dart b/pkg/unittest/test/unittest_test.dart
index 31d5bcc285f2f625b6e49c1cf168ae52bd48cc01..7f62c503cf542d84348c78d4fcfb0ebb6aefeb81 100644
--- a/pkg/unittest/test/unittest_test.dart
+++ b/pkg/unittest/test/unittest_test.dart
@@ -294,6 +294,11 @@ runTest() {
       });
       test('foo6', () {
       });
+    } else if (testName == 'testCases immutable') {
+      test(testName, () {
+        expect(() => testCases.clear(), throwsUnsupportedError);
+        expect(() => testCases.removeLast(), throwsUnsupportedError);
+      });
     }
   });
 }
@@ -329,7 +334,8 @@ main() {
     'middle exception test',
     'async setup/teardown test',
     'test returning future',
-    'test returning future using Timer'
+    'test returning future using Timer',
+    'testCases immutable'
   ];
 
   expected = [
@@ -376,6 +382,7 @@ main() {
         'fail2:failure:'
         'error2:Callback called more times than expected (1).:'
         'foo6'),
+    buildStatusString(1, 0, 0, 'testCases immutable'),
   ];
 
   actual = [];