Robolectric : Build failed with Null Pointer Exception

Question

I recently started to work on the Robolectric unit testing framework for my android apps. I am using Android Studio IDE for this all.

I have made MainActivity.java where there is button R.id.clickButton, I am able to run that app in my phone/emulator and working fine.

I have made MainActivityTest.java where I am trying to see is button not null like below

private MainActivity activity;

@Before
public void setup() {
    activity = Robolectric.buildActivity(MainActivity.class).get();
}

@Test
public void shouldFail() {
    assertTrue(true);
}

@Test
public void shouldNotBeNull() {
    assertThat(activity).isNotNull();

    Button button = (Button) activity.findViewById(R.id.clickButton);
    assertThat(button).isNotNull();

}

When I execute the test using command line then build failed at Button button = (Button) activity.findViewById(R.id.clickButton); with an error trace. I could not find why it so. Guys look this and hoping you will reply me soon.

StackTrace

java.lang.NullPointerException
    at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:132)
    at android.view.ViewGroup.initViewGroup(ViewGroup.java:447)
    at android.view.ViewGroup.__constructor__(ViewGroup.java:417)
    at android.view.ViewGroup.<init>(ViewGroup.java:416)
    at android.widget.FrameLayout.<init>(FrameLayout.java:93)
    at org.robolectric.tester.android.view.RoboWindow$2.<init>(RoboWindow.java:231)
    at org.robolectric.tester.android.view.RoboWindow.createDecorView(RoboWindow.java:231)
    at org.robolectric.tester.android.view.RoboWindow.access$000(RoboWindow.java:30)
    at org.robolectric.tester.android.view.RoboWindow$1.run(RoboWindow.java:222)
    at org.robolectric.shadows.ShadowLooper.runPaused(ShadowLooper.java:256)
    at org.robolectric.tester.android.view.RoboWindow.getDecorView(RoboWindow.java:220)
    at org.robolectric.tester.android.view.RoboWindow.findViewById(RoboWindow.java:292)
    at org.robolectric.shadows.ShadowActivity.findViewById(ShadowActivity.java:312)
    at android.app.Activity.findViewById(Activity.java)
    at com.example.robolectrichelloworld.MainActivityTest.shouldNotBeNull(MainActivityTest.java:41)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.robolectric.RobolectricTestRunner$2.evaluate(RobolectricTestRunner.java:241)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.robolectric.RobolectricTestRunner$1.evaluate(RobolectricTestRunner.java:177)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:86)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:49)
    at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:69)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:50)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.messaging.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
    at org.gradle.messaging.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
    at com.sun.proxy.$Proxy2.processTestClass(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:103)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
    at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.messaging.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:355)
    at org.gradle.internal.concurrent.DefaultExecutorFactory$StoppableExecutorImpl$1.run(DefaultExecutorFactory.java:64)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)

Answer 1

I solved the problem by simply extend the class by Activity. My activity was extending ActionBarActivity that was creating the issue.

Answer 2

Try to insert the call to create() after Robolectric.buildActivity(...):

@Before
public void setup()  {
    activity = Robolectric.buildActivity(MainActivity.class).create().get();
}