title: What is causing this mockito exception?
body: <p>I am in the process of creating test cases for a project. How the project is designed, it is difficult to go ahead and do simple unit tests and seems to be missing a dependency in order to use Mockito for mocking functions and objects. Here is what I have:</p>
  
  <pre><code>@RunWith(SpringRunner.class)
  public class RequestHandlerTest {
      private byte[] buffer;
      private Connection conn;
      private Server server;
  
      @Mock ResponseHandler response;
      @Mock Services serviceImpl;
      @InjectMocks RequestHandler request;
  
      @Before
      // This just creates the buffer in order to simulate sending and 
      // receiving a response across a server and client
      public void createRequests(); 
  
      @After
      public void cleanUpBuffer(); // Cleans up buffer after test
  
      @Test
      public void TestReceiveMessage() {
          doNothing().when(response.updataCache(conn, reqID));
          ... // Do nothing for service function
          handler.receiveMsg(conn, buffer);
          // Verify request
      }
  }
  </code></pre>
  
  <p>Now whenever I run the test I am getting the following exception:</p>
  
  <pre><code> org.mockito.exceptions.base.MockitoException: At the moment you cannot provide own implementations of MockHandler.
  Please see the javadocs for the MockMaker interface.
      at org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener.initMocks(MockitoTestExecutionListener.java:68)
      at org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener.prepareTestInstance(MockitoTestExecutionListener.java:53)
      at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:246)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:227)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:246)
      at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at 
  
      org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
          at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
          at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
          at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
          at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
          at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
          at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
          at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
          at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
          at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
  </code></pre>
  
  <p>I am not sure what is causing this and what needs to be done to resolve this. I tried setting initializing Mockito, changing @Mock to @MockBean with @Autowired, and also tried just setting my values using a wrapper class. Is there something I could be missing? I have never seen this before. </p>