I’m trying to test a Java application using Mockito, and I encountered the doReturn method. I’m not entirely sure how it differs from the when-thenReturn syntax. Could someone provide a clear example of how to utilize doReturn in a testing scenario? Specifically, I’d like to understand the typical cases where doReturn is more appropriate than other stubbing methods.
Hey there! When using Mockito for testing, doReturn is useful if you need to stub a method that has a side effect or when dealing with final methods. For instance, if a method throws an exception when evaluated, you’ll want to use doReturn instead of when-thenReturn because it doesn’t actually call the method while setting up stubbing. Just use it like this: doReturn(value).when(mock).method(). It’s particularly handy when you can’t or don’t want to allow the method call to proceed during setup.
In my experience, doReturn is a lifesaver when working with final classes or methods, which Mockito can’t mock using the usual when(thenReturn) syntax. Imagine you’re dealing with a legacy library where some methods are final—doReturn comes to the rescue here. Its syntax looks like this: doReturn(expected).when(mockedObject).methodCall(). While it might feel a bit backward compared to when(thenReturn), it’s perfect for bypassing issues where method execution needs to be avoided during mock setup.
From a testing perspective, doReturn is crucial when setting up mocks that could cause issues if method execution occurs. I had a scenario with a method performing actions on files; I wanted to mock its return value without altering files. By using doReturn(myValue).when(myMock).myMethod(), I avoided actual file operations that would have otherwise resulted from method evaluation. This approach saves you from unintended side effects during testing. It’s a bit different syntax-wise but invaluable when dealing with method calls you want to suppress.