How to Inject Prototype bean in Mockito

Question

I am using InjectMocks and Spy annotations for injecting a prototype bean.

However the inject bean behaves like singleton bean. Is there any way to inject a prototype scoped bean in Mockito?

I am running JUnit with SpringJUnit4ClassRunner and init mocks using MockitoAnnotations.initMocks(this).

Answer 1

That's because Mockito creates your injected objects at compile time. If you want a prototype-like behavior, you need to switch to using answers.

For example, assume that your Spring application has a prototype bean called Foo and your code is doing something like this multiple times:

ctx.getBean("Foo");

Since Foo is a prototype, every time getBean() is called, a new instance of Foo is returned by Spring.

Now, in your Mockito test you mocked the ctx to spoof the getBean() and return your own pre-configured instance of Foo.

if you set up your test like below, no matter how many times your code calls ctx.getBean(), the same instance of Foo will be returned:

Foo foo = new Foo();
decorateFoo(foo);
when(ctx.getBean("Foo")).thenReturn(foo);

This is how you can achieve a prototype-like behavior in your test:

when(ctx.getBean("Foo")).then(new FooAnswer());

private class FooAnswer implements Answer<Foo> {
    @Override
    public Foo answer(InvocationOnMock invocationOnMock) throws Throwable {
                return new Foo(); // and configure as needed
    }
}