Robolectric unit test for fragment fails intermitently with ClassNotFoundException exception - unit-testing

Question

I have a build on TeamCity that runs unit tests via Gradle. Intermitentlly, tests that involve fragments or activities fail with a ClassNotFoundException for classes like android.support.v4.app.FragmentTransitionCompat21$ViewRetriever or android.support.v4.app.ActivityCompat21$SharedElementCallback21. The tests fail when starting the fragment, and I've tried all of the methods to start a fragment from this question - How can I test fragments with Robolectric?.
Here's an example for a test:
#Test
public void ContactSupportFragment_CallBtnClicked_CallWasMade() throws Exception
{
ContactSupportFragment fragment = new ContactSupportFragment();
startFragment(fragment);
LinearLayout btnCall = (LinearLayout) fragment.getView().findViewById(R.id.contact_support_call_btn);
btnCall.performClick();
Mockito.verify(techSupportCall, Mockito.times(1)).call(Mockito.any(Context.class),
Mockito.eq(Robolectric.application.getString(R.string.tech_support_phone_number)));
}
Here's an example for a stack trace:
java.lang.NoClassDefFoundError: android/support/v4/app/FragmentTransitionCompat21$ViewRetriever
at android.support.v4.app.FragmentManagerImpl.beginTransaction(FragmentManager.java:481)
at org.robolectric.util.FragmentTestUtil.startFragment(FragmentTestUtil.java:25)
at com.asurion.solutohome.callsupport.ContactSupportFragmentTest.ContactSupportFragment_CallBtnClicked_CallWasMade(ContactSupportFragmentTest.java:70)
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.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.robolectric.RobolectricTestRunner$2.evaluate(RobolectricTestRunner.java:236)
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 org.robolectric.RobolectricTestRunner$1.evaluate(RobolectricTestRunner.java:158)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:86)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:49)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:69)
at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:48)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.messaging.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
at org.gradle.messaging.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
at com.sun.proxy.$Proxy2.processTestClass(Unknown Source)
at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:105)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.messaging.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:360)
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:745)
Caused by: java.lang.ClassNotFoundException: android.support.v4.app.FragmentTransitionCompat21$ViewRetriever
at org.robolectric.bytecode.AsmInstrumentingClassLoader.loadClass(AsmInstrumentingClassLoader.java:88)
at android.support.v4.app.FragmentManagerImpl.$$robo$$FragmentManagerImpl_917e_beginTransaction(FragmentManager.java:481)
at android.support.v4.app.FragmentManagerImpl.beginTransaction(FragmentManager.java)
at org.robolectric.util.FragmentTestUtil.startFragment(FragmentTestUtil.java:25)
at com.asurion.solutohome.callsupport.ContactSupportFragmentTest.ContactSupportFragment_CallBtnClicked_CallWasMade(ContactSupportFragmentTest.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
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.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.robolectric.RobolectricTestRunner$2.evaluate(RobolectricTestRunner.java:236)
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 org.robolectric.RobolectricTestRunner$1.evaluate(RobolectricTestRunner.java:158)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:86)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:49)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:69)
at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:48)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.messaging.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
at org.gradle.messaging.dispatch.ProxyDispatchAdapter$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:105)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
It hasn't happened locally yet, only on the TeamCity agent, however I haven't found anything different between my machine and the agent (same SDK, same Gradle build etc.).
What can cause these exceptions?

Answer 1

So following #EugenMartynov's suggestion I added an additional assemble build step to my Teamcity build before building running the tests and so far all the builds pass. It seems that Robolectric indeed has some issues with CI builds.
So to summarize, instead of building once and running tests, my build runs:
clean and build
build again and run tests
All of the tests pass every build.

Answer 2

I am not much into the topic of Robolectric, but the stacktrace you sent looks like you forgot to add the binaries or the jar, which includes the class android.support.v4.app.FragmentTransitionCompat21 (i think this class is included in the android SDK), to your classpath.

Answer 3

As per #Fastas answer. You can run
gradle test
This will resolve the issue, but as for it's exact cause, it is as of yet unknown.
For my own part, I think this is related to dependencies from my app project not fully resolving the first build of an exterior app-test project. I am using the following code in app-test/build.gradle.
dependencies {
// other dependencies ...
compile project(':app')
testCompile androidModule.android.applicationVariants.toList().first().javaCompile.classpath
testCompile androidModule.android.applicationVariants.toList().first().javaCompile.outputs.files
testCompile files(androidModule.plugins.findPlugin("com.android.application").getBootClasspath())
}
Above, possibly classpath or outputs.files is not fully resolved until the assemble task finishes.
Update: March 23, 2015
Moving my test suite to the experimental test support within the app module resolved this issue for me.