我读过各种关于测试中模仿和存根的文章,包括Martin Fowler的《Mocks Aren't Stubs》,但我仍然不理解其中的区别。
当前回答
下面是对每一个的描述,然后是真实世界的样本。
Dummy - just bogus values to satisfy the API. Example: If you're testing a method of a class which requires many mandatory parameters in a constructor which have no effect on your test, then you may create dummy objects for the purpose of creating new instances of a class. Fake - create a test implementation of a class which may have a dependency on some external infrastructure. (It's good practice that your unit test does NOT actually interact with external infrastructure.) Example: Create fake implementation for accessing a database, replace it with in-memory collection. Stub - override methods to return hard-coded values, also referred to as state-based. Example: Your test class depends on a method Calculate() taking 5 minutes to complete. Rather than wait for 5 minutes you can replace its real implementation with stub that returns hard-coded values; taking only a small fraction of the time. Mock - very similar to Stub but interaction-based rather than state-based. This means you don't expect from Mock to return some value, but to assume that specific order of method calls are made. Example: You're testing a user registration class. After calling Save, it should call SendConfirmationEmail.
存根和Mock实际上是Mock的子类型,两者都交换了实际实现和测试实现,但出于不同的、特定的原因。
其他回答
Stub帮助我们运行测试。怎么做?它给出了有助于运行测试的值。这些值本身不是真实的,我们创建这些值只是为了运行测试。例如,我们创建一个HashMap来提供与数据库表中的值相似的值。因此,我们不直接与数据库交互,而是与Hashmap交互。
Mock是一个运行测试的伪对象。我们在这里输入assert。
存根用于您在测试中设置的具有预期返回值的方法。 mock用于void方法,这些方法在调用时的Assert中进行验证。
Stubs vs. Mocks Stubs provide specific answers to methods calls ex: myStubbedService.getValues() just return a String needed by the code under test used by code under test to isolate it cannot fail test ex: myStubbedService.getValues() just returns the stubbed value often implement abstract methods Mocks "superset" of stubs; can assert that certain methods are called ex: verify that myMockedService.getValues() is called only once used to test behaviour of code under test can fail test ex: verify that myMockedService.getValues() was called once; verification fails, because myMockedService.getValues() was not called by my tested code often mocks interfaces
使用一个心智模型确实帮助我理解了这一点,而不是所有的解释和文章,这些都不能“理解”。
想象一下,你的孩子桌子上有一个玻璃盘子,他开始玩它。现在,你害怕它会破裂。所以,你给了他一个塑料盘子。这将是一个Mock(相同的行为,相同的接口,“更软的”实现)。
现在,假设你没有塑料替代品,所以你解释说“如果你继续玩它,它会碎的!”这是一个Stub,您预先提供了一个预定义的状态。
哑巴就是他根本不用的叉子…间谍可能是提供你已经使用过的有效解释。
模拟:帮助模拟和检查结果交互。这些交互 SUT调用它的依赖项来改变它们的状态。
存根:帮助模拟传入的交互。这些相互作用称为 SUT对其依赖项进行处理以获取输入数据。
来源:单元测试原则、实践和模式- Manning
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