BackendRunner mockedRunner = mock(BackendRunner.class);

// Mock method runProcess() to do nothing
doAnswer(new Answer<Void>() {
    public Void answer(InvocationOnMock invocation) {
        Object[] args = invocation.getArguments();
        System.out.println("called with arguments: " + Arrays.toString(args));
        return null;
    }
}).when(mockedRunner).runProcess(any());