Robolectric fails on command line but succeeds in Android Studio

Question

I have a test where I use Robolectric which succeeds in Android Studio, but does not on the command line.

I use Robolectric 4.2 and the test involves a cipher which I partially mock for this test.

//How the cipher is created
val mockCipher = object : Cipher(MockCipherSpi(), null, null) {}

The MockCipher basically just returns the unencrypted input:

class MockCipherSpi : CipherSpi() {
...
    private val algorithmParametersSpi: AlgorithmParametersSpi? = object : AlgorithmParametersSpi() {
        ...
        override fun <T : AlgorithmParameterSpec?> engineGetParameterSpec(paramSpec: Class<T>?): T {
            return IvParameterSpec(byteArrayOf()) as T
        }
    }
    ...
    override fun engineGetParameters(): AlgorithmParameters {
        return object : AlgorithmParameters(algorithmParametersSpi, null, null) {
            init {
                init(byteArrayOf())
            }
        }
    }
}

The reason my test fails is that I get a null pointer exception when I try to get the IV from the cipher:

cipher.parameters.getParameterSpec(IvParameterSpec::class.java).iv

This works perfectly fine for Android Studio and I can even debug it, but running it from the command line with ./gradlew test this fails.

java.lang.NullPointerException
at javax.crypto.Cipher.<init>(Cipher.java:268)
at the place where I try to access the iv
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$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.robolectric.RobolectricTestRunner$HelperTestRunner$1.evaluate(RobolectricTestRunner.java:601)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.robolectric.internal.SandboxTestRunner$2.evaluate(SandboxTestRunner.java:260)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:130)
at org.robolectric.internal.SandboxTestRunner.runChild(SandboxTestRunner.java:42)
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.internal.SandboxTestRunner$1.evaluate(SandboxTestRunner.java:84)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.runTestClass(JUnitTestClassExecutor.java:116)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:59)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:39)
at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestClassProcessor.processTestClass(AbstractJUnitTestClassProcessor.java:66)
at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:51)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
at com.sun.proxy.$Proxy1.processTestClass(Unknown Source)
at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:109)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:146)
at org.gradle.internal.remote.internal.hub.MessageHubBackedObjectConnection$DispatchWrapper.dispatch(MessageHubBackedObjectConnection.java:128)
at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:404)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:63)
at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:46)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:55)
at java.lang.Thread.run(Thread.java:748)

It seems there are two javax.crypto.Cipher one from the in the android.jar and one in the jce.jar I assume that AS is using one and the gradle command the other.

Do I have to tell gradle to use an other jar or can I solve this problem otherwise?

Answer 1

You are trying to use a class from the android SDK in a desktop test. That's always going to fail. The Android SDK has classes that simply aren't available in the Java Development Kit. The Android jar provides just an empty API for development purposes, but to run the programs, you need to execute them into an android device. In this case, you would need to either mock the entire call, or locate an equivalent desktop implementation and replace the android calls with the desktop ones during the test (maybe by splitting your class in two, logic and API access for example). Given that the methods you are running are exposing a native (C level) api, mocking the entire API call looks like the fastest way to solve this into the test.