mockc | Completely type-safe compile-time mock generator for Go | Mock library

When you run the test with spring runner, you must specify what exactly would you like to load as beans (read, let spring know what exactly should be included into the application context).

Usually this can be done with @ContextConfiguration annotation.

I suspect that since you don't specify this annotation, spring doesn't really loads any of your components (A, B, C in the question, etc).

Now @MockBean basically allows "altering" the application context for test purposes. It does so by providing a mock instead of a real bean that should have been loaded in "regular" application context.

In this case, there is no point to call MockitoAnnotations.initMocks(this); Spring will inject the mocks by itself once everything is configured properly.