Remove a test for testCases being immutable.

pkg/unittest/test/unittest_test.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.
 
 // TODO(gram):
 // Unfortunately I can't seem to test anything that involves timeouts, e.g.
 // insufficient callbacks, because the timeout is controlled externally
 // (test.dart?), and we would need to use a shorter timeout for the inner tests
 // so the outer timeout doesn't fire. So I removed all such tests.
 // I'd like to revisit this at some point.
@@ skipping 274 matching lines @@
               excesscallback();
               excesscallback();
               excesscallback();
               callback();
             });
           });
         });
       });
       test('foo6', () {
       });
-    } else if (testName == 'testCases immutable') {
-      test(testName, () {
-        expect(() => testCases.clear(), throwsUnsupportedError);
-        expect(() => testCases.removeLast(), throwsUnsupportedError);
-      });
     } else if (testName == 'runTests without tests') {
       runTests();
     }
   });
 }
 
 main() {
   var tests = {
     'single correct test': buildStatusString(1, 0, 0, 'single correct test'),
     'single failing test': buildStatusString(0, 1, 0, 'single failing test',
@@ skipping 36 matching lines @@
         'error2:Callback called more times than expected (1).:'
         'fail2:failure:'
         'foo5'),
     'test returning future using Timer': buildStatusString(2, 4, 0,
         'successful::'
         'fail1:Expected: <false> but: was <true>.:'
         'error1:Callback called more times than expected (1).:'
         'fail2:failure:'
         'error2:Callback called more times than expected (1).:'
         'foo6'),
-    'testCases immutable':
-        buildStatusString(1, 0, 0, 'testCases immutable'),
     'runTests without tests': buildStatusString(0, 0, 0, null)
   };
 
   tests.forEach((String name, String expected) {
     test(name, () => spawnFunction(runTest)
         .call(name)
         .then((String msg) => expect(msg.trim(), equals(expected))));
     });
 }