public void Test_Delete_DeletesCategoryFromDatabase()
    {
      //Arrange
      Category testCategory1 = new Category("Home stuff");
      testCategory1.Save();
      Category testCategory2 = new Category("Work stuff");
      testCategory2.Save();

      //Act
      testCategory1.DeleteCategory();
      List<Category> resultCategories = Category.GetAll();
      List<Category> testCategoryList = new List<Category> {testCategory2};

      //Assert
      Assert.Equal(testCategoryList,resultCategories);
    }
    public void Test_Delete_DeletesCategoryAssociatonsFromDatabase()
    {
      //Arrange
      DateTime testDate = new DateTime(2017, 2, 21);
      Task testTask= new Task("Mow the lawn", testDate);
      testTask.Save();

      Category testCategory = new Category("Household chores");
      testCategory.Save();

      //Act
      testCategory.AddTask(testTask);
      testCategory.DeleteCategory();
      List<Category> resultTaskCategories = testTask.GetCategories();
      List<Category> testTaskCategories = new List<Category>{};

      //Assert
      Assert.Equal(testTaskCategories, resultTaskCategories);
    }