private void InvokeDiffTool(
            ITestFile expectedFile,
            ITestFile actualFile,
            Exception testRunnerException)
        {
            try
            {
                _diffTool.CompareFiles(expectedFile, actualFile);
            }
            catch (Exception ex)
            {
                throw new DiffAssertException(
                          expectedFile,
                          actualFile,
                          testRunnerException,
                          ex.Message);
            }

            throw new DiffAssertException(
                      expectedFile,
                      actualFile,
                      testRunnerException);
        }