What is the best way to verify a method was called on an object created within a method using Mockito?

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Another solution is to spy on the Foo object itself, allowing you to verify the interactions with the Bar object through the spy. This is less common and more of a workaround if you don’t want to modify the original code.

Test Code with Mockito Spy:

import static org.mockito.Mockito.*;

public class FooTest {
    @Test
    public void testFoo() {
        // Spy on the Foo class (this is not a mock, it's a partial mock)
        Foo spyFoo = spy(new Foo());

        // Mock the Bar instance within the Foo class
        Bar mockBar = mock(Bar.class);

        // Replace the Bar instance inside Foo with the mock
        doReturn(mockBar).when(spyFoo).createBar();

        // Call the method under test
        spyFoo.foo();

        // Verify the method was called on the mock Bar
        verify(mockBar, times(1)).someMethod();
    }
}

In this example, you spy on the Foo object and override the method that creates Bar. This approach is a bit more complex and usually requires you to provide an additional method like createBar() that can be mocked.