public void Test_Complete_CompletesTaskWhenDone()
        {
            //Arrange
              string testDescription = "Mow the lawn";
              DateTime? taskDate = new DateTime(2016, 7, 12);
              Task testTask = new Task(testDescription, taskDate);
              testTask.Save();

              //Act
              testTask.Complete();
              bool result = testTask.IsDone();

              //Assert
              Assert.Equal(true, result);
        }