title: NullPointerException when testing resource in dropwizard with mockito
body: <p>I built a restful API with dropwizard. And now I want to test it with <a href="http://www.dropwizard.io/0.9.2/docs/manual/testing.html" rel="nofollow">what dropwizard document provided</a>. </p>
  
  <pre><code>public class BlogCommentResourceTest {
  private static final BlogCommentDAO dao = mock(BlogCommentDAO.class);
  private final BlogComment blogComment = new BlogComment(1, "url", "comment", new Date(), "name");
  @ClassRule
  public static final ResourceTestRule resources = ResourceTestRule.builder()
          .addResource(new BlogCommentResource(dao)).build();
  List&lt;BlogComment&gt; list = new ArrayList&lt;BlogComment&gt;();
  
  @Before
  public void setUp(){
      list.add(blogComment);
  
      when(dao.getLast()).thenReturn(blogComment);
      when(dao.getAll(POJOs.BlogCommentPOJO.toString())).thenReturn(list);
  }
  @After
  public void tearDown(){
      reset(dao);
  }
  @Test
  public void getLast(){
      assertThat(resources.client().target("/blogcomments").request().get(List.class))
              .isEqualTo(list);
      verify(dao.getAll(POJOs.BlogCommentPOJO.toString()), times(1));
  }
  </code></pre>
  
  <p>}</p>
  
  <p>This is the method I want to test.</p>
  
  <pre><code>enter code here
  </code></pre>
  
  <p>And error message is shown as below:</p>
  
  <pre><code>java.lang.NullPointerException
  at dao.DAOBase.getAll(DAOBase.java:37)
  at dao.BlogCommentDAO.getAll(BlogCommentDAO.java:19)
  at resource.BlogCommentResourceTest.setUp(BlogCommentResourceTest.java:29)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:498)
  at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
  at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
  at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
  at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
  at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
  at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
  at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
  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 io.dropwizard.testing.junit.ResourceTestRule$1.evaluate(ResourceTestRule.java:202)
  at org.junit.rules.RunRules.evaluate(RunRules.java:20)
  at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
  at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
  at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119)
  at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
  at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
  at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:498)
  at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
  </code></pre>
  
  <p>Somebody know what happened? Why it is the DAOBase that throw a null pointer? My unit test for all of dao shows they works well.</p>