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POMockito: Mocking "Blackbox" Dependencies
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copied!<p>So I have been asked to read up on mocking and BDD for our development team and play around with mocks so as to improve a handful of our existing unit tests (as an experiment).</p> <p>I have ultimately chosen to go with Mockito for a number of reasons (some outside the scope of my control), but namely because it supports both stubbing and mocking for instances when mocking would not be appropriate.</p> <p>I have spent all day learning about Mockito, mocking (in general) and BDD. And now I am ready to dig in and start augmenting our unit tests.</p> <p>So we have a class called <code>WebAdaptor</code> that has a <code>run()</code> method:</p> <pre><code>public class WebAdaptor { private Subscriber subscriber; public void run() { subscriber = new Subscriber(); subscriber.init(); } } </code></pre> <p><strong>Please note:</strong> I do not have a way to modify this code (for reasons outside the scope of this question!). Thus I do <em>not</em> have the ability to add a setter method for <code>Subscriber</code>, and thus it can be thought of as an unreachable "blackbox" inside of my <code>WebAdaptor</code>.</p> <p>I want to write a unit test which incorporates a <code>Mockito</code> mock, and uses that mock to <code>verify</code> that executing <code>WebAdaptor::run()</code> causes <code>Subscriber::init()</code> to be called.</p> <p>So here's what I've got so far (inside <code>WebAdaptorUnitTest</code>):</p> <pre><code>@Test public void runShouldInvokeSubscriberInit() { // Given Subscriber mockSubscriber = mock(Subscriber.class); WebAdaptor adaptor = new WebAdaptor(); // When adaptor.run(); // Then verify(mockSubscriber).init(); } </code></pre> <p>When I run this test, the actual <code>Subscriber::init()</code> method gets executed (I can tell from the console output and seeing files being generated on my local system), <em>not</em> the <code>mockSubscriber</code>, which shouldn't do (or return) anything.</p> <p>I have checked and re-checked: <code>init</code> is <code>public</code>, is neither <code>static</code> or <code>final</code>, and it returns <code>void</code>. According to the docs, Mockito should have no problem mocking this object.</p> <p>So it got me thinking: do I need to explictly associate the <code>mockSubscriber</code> with the <code>adaptor</code>? If this is a case, then ordinarily, the following would normally fix it:</p> <pre><code>adaptor.setSubscriber(mockSubscriber); </code></pre> <p>But since I cannot add any such setter (please read my note above), I'm at a loss as to how I could force such an association. So, several very-closely-related questions:</p> <ul> <li>Can anyone confirm that I've set the test up correctly (using the Mockito API)?</li> <li>Is my suspicion about the missing setter correct? (Do I need to associate these objects via a setter?)</li> <li>If my above suspicion is true, and I can't modify <code>WebAdaptor</code>, are there any circumventions at my dispose?</li> </ul> <p>Thanks in advance!</p>

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