Sample project to reproduce mockk/robolectric incompatibility

Summary:

Using mockk(relaxed=true) in a test setUp() results in a ClassCastException, when at least two test methods are run, and the second test has a @Config(sdk=[??]) annotation.

Steps to reproduce:

• Run ./gradlew testDebugUnitTest
• Expected behavior: tests pass
• Actual behavior: testMockk2() fails:

  io.mockk.MockKException: Can't instantiate proxy for class com.example.robolectricmockk.Foo
  	at io.mockk.impl.instantiation.JvmMockFactory.newProxy(JvmMockFactory.kt:64)
  	at io.mockk.impl.instantiation.AbstractMockFactory.newProxy$default(AbstractMockFactory.kt:29)
  	at io.mockk.impl.instantiation.AbstractMockFactory.mockk(AbstractMockFactory.kt:59)
  	at com.example.robolectricmockk.ExampleUnitTest.setUp(ExampleUnitTest.kt:53)
  	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$1.runReflectiveCall(FrameworkMethod.java:50)
  	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
  	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
  	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
  	at org.robolectric.RobolectricTestRunner$HelperTestRunner$1.evaluate(RobolectricTestRunner.java:575)
  	at org.robolectric.internal.SandboxTestRunner$2.lambda$evaluate$0(SandboxTestRunner.java:263)
  	at org.robolectric.internal.bytecode.Sandbox.lambda$runOnMainThread$0(Sandbox.java:89)
  	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
  	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
  	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
  	at java.lang.Thread.run(Thread.java:748)
  Caused by: io.mockk.proxy.MockKAgentException: Instantiation exception
  	at io.mockk.proxy.jvm.ProxyMaker.proxy(ProxyMaker.kt:54)
  	at io.mockk.impl.instantiation.JvmMockFactory.newProxy(JvmMockFactory.kt:34)
  	... 18 more
  Caused by: java.lang.ClassCastException: Cannot cast com.example.robolectricmockk.Foo to com.example.robolectricmockk.Foo
  	at java.lang.Class.cast(Class.java:3369)
  	at io.mockk.proxy.jvm.ObjenesisInstantiator.instanceViaObjenesis(ObjenesisInstantiator.kt:73)
  	at io.mockk.proxy.jvm.ObjenesisInstantiator.instance(ObjenesisInstantiator.kt:42)
  	at io.mockk.proxy.jvm.ProxyMaker.instantiate(ProxyMaker.kt:75)
  	at io.mockk.proxy.jvm.ProxyMaker.proxy(ProxyMaker.kt:42)
  	... 19 more
  

Additional information:

• Same behavior is observed using java 8 or java 14
• Same behavior if mockk is used inside setUp() or inside the test method directly
• Same behavior regardless of the value of the sdk in the @Config(sdk=[??]) annotation in testMockk2()
  • Exception: when running with java 14, and specifying sdk=[29], both tests pass
• Running testMockk2() in isolation works
• Remove the @Config(sdk=[28]) annotation from testMockk2() and both tests will pass
• Both tests pass using robolectric 4.3.1 and java 8