Return ImmutableSet from JMock'd object causes UndeclaredThrowableException

Question

Here's my unit test that I expect to pass:

import static org.junit.Assert.assertEquals;

import org.jmock.Expectations;
import org.jmock.Mockery;
import org.junit.Test;

import com.google.common.collect.ImmutableSet;

public class JMockTest {

    @Test
    public void test() {
        Mockery mockery = new Mockery();

        final Foo foo = mockery.mock(Foo.class);
        mockery.checking(new Expectations() {{
            oneOf(foo).bar(); will(returnValue(ImmutableSet.<Long>of()));
        }});

        ImmutableSet<Long> result = foo.bar();
        assertEquals(ImmutableSet.<Long>of(), result);
    }

    interface Foo {
        ImmutableSet<Long> bar();
    }

}

However, it throws this error instead:

java.lang.reflect.UndeclaredThrowableException
    at $Proxy3.bar(Unknown Source)
    at JMockTest$1.<init>(JMockTest.java:17)
    at JMockTest.test(JMockTest.java:16)
    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:497)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: java.lang.IllegalAccessException: Class org.jmock.internal.ReturnDefaultValueAction can not access a member of class com.google.common.collect.ImmutableSet with modifiers ""
    at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:102)
    at java.lang.Class.newInstance(Class.java:436)
    at org.jmock.internal.ReturnDefaultValueAction.collectionOrMapInstanceFor(ReturnDefaultValueAction.java:87)
    at org.jmock.internal.ReturnDefaultValueAction.invoke(ReturnDefaultValueAction.java:77)
    at org.jmock.internal.InvocationToExpectationTranslator.invoke(InvocationToExpectationTranslator.java:20)
    at org.jmock.internal.FakeObjectMethods.invoke(FakeObjectMethods.java:38)
    at org.jmock.lib.JavaReflectionImposteriser$1.invoke(JavaReflectionImposteriser.java:33)
    ... 26 more

It seems that JMock is internally attempting to instantiate an ImmutableSet, even though I provided one for it.

See ReturnDefaultValueAction:

private Object collectionOrMapInstanceFor(Class<?> returnType) throws Throwable {
  return returnType.isInterface() ? instanceForCollectionType(returnType) : returnType.newInstance();
}

returnType.isInterface() is false b/c it's a ImmutableSet, so JMock calls ImmutableSet.newInstance(), which fails b/c ImmutableSet does not have an accessible constructor.

I assume that people other than me have mocked interfaces that return guava immutable collection objects before, or interfaces that return classes with no visible constructor. How do you deal with this in JMock?

EDIT: This is JMock 2.6.0

EDIT2: This works in JMock 2.8.2!

Answer 1

This seems like a bug with your version of JMock, 2.6.0, as you've described it. Upgrade to the latest, currently 2.8.2. The issue will go away.