anchor.diff:    await runPassingTest(testDisappearingLibrary);
     await runPassingTest(testDeferredLibrary);
     await runPassingTest(testStrongModeMixins);
  +  await runFailingTest(
  +      testStrongModeMixins2,
  +      "testStrongModeMixins2_a.dart: Error: "
  +      "The parameter 'value' of the method 'A::child' has type");
   }
   
   void runFailingTest(dynamic test, String expectContains) async {
  
positive.code:   } finally {
      outDir.deleteSync(recursive: true);
    }
  }
  
  /// Compile in strong mode. Invalidate a file so type inferrer starts
  
negative.code:   var options = new CompilerOptions()
      ..sdkRoot = sdkRoot
      ..librariesSpecificationUri = Uri.base.resolve("sdk/lib/libraries.json")
      ..onProblem = (LocatedMessage message, Severity severity, String formatted,
          int line, int column) {
        if (severity == Severity.error || severity == Severity.warning) {
          Expect.fail("Unexpected error: $formatted");
        }
      }
      ..strongMode = false;
    return options;
  }
  