Mocking with explicit constructor fails with varargs parameter

[jeff303]

Consider the following test

import org.junit.Test;
import org.mockito.Mockito;

public class MockitoTest {

    private static class A {
        A(String a, int b, AutoCloseable... c) {
            System.out.println("Constructor called");
        }
    }

    @Test
    public void testIssue() {

        AutoCloseable c = () -> {
            System.out.println("Closing");
        };
        A a = Mockito.mock(A.class, Mockito.withSettings().useConstructor("hi", 1, new AutoCloseable[] {c}));

    }
}

On Temurin JDK 11, OS X, mockito-core 4.4.0, this fails with:

Unable to create mock instance of type 'A'
org.mockito.exceptions.base.MockitoException: Unable to create mock instance of type 'A'
	at MockitoTest.testIssue(MockitoTest.java:20)
	at java.base@11.0.14/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base@11.0.14/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base@11.0.14/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base@11.0.14/java.lang.reflect.Method.invoke(Method.java:566)
	at app//org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at app//org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at app//org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at app//org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at app//org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at app//org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at app//org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at app//org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at app//org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at app//org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at app//org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at app//org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at app//org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at app//org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at app//org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at app//org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.runTestClass(JUnitTestClassExecutor.java:110)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:58)
	at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecutor.execute(JUnitTestClassExecutor.java:38)
	at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestClassProcessor.processTestClass(AbstractJUnitTestClassProcessor.java:62)
	at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:51)
	at java.base@11.0.14/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base@11.0.14/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base@11.0.14/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base@11.0.14/java.lang.reflect.Method.invoke(Method.java:566)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
	at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
	at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
	at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
	at com.sun.proxy.$Proxy2.processTestClass(Unknown Source)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:176)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
	at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
	at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:133)
	at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:71)
	at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
	at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
Caused by: org.mockito.creation.instance.InstantiationException: 
Unable to create instance of 'A'.
Please ensure the target class has a constructor that matches these argument types: [java.lang.String, java.lang.Integer, [Ljava.lang.AutoCloseable;] and executes cleanly.
	... 44 more
Caused by: java.lang.reflect.InvocationTargetException
	at org.mockito.internal.util.reflection.InstrumentationMemberAccessor.newInstance(InstrumentationMemberAccessor.java:198)
	at org.mockito.internal.util.reflection.InstrumentationMemberAccessor.newInstance(InstrumentationMemberAccessor.java:161)
	at org.mockito.internal.util.reflection.ModuleMemberAccessor.newInstance(ModuleMemberAccessor.java:42)
	at org.mockito.internal.creation.instance.ConstructorInstantiator.invokeConstructor(ConstructorInstantiator.java:70)
	at org.mockito.internal.creation.instance.ConstructorInstantiator.withParams(ConstructorInstantiator.java:53)
	at org.mockito.internal.creation.instance.ConstructorInstantiator.newInstance(ConstructorInstantiator.java:39)
	at org.mockito.internal.creation.bytebuddy.InlineDelegateByteBuddyMockMaker.doCreateMock(InlineDelegateByteBuddyMockMaker.java:358)
	at org.mockito.internal.creation.bytebuddy.InlineDelegateByteBuddyMockMaker.createMock(InlineDelegateByteBuddyMockMaker.java:328)
	at org.mockito.internal.creation.bytebuddy.InlineByteBuddyMockMaker.createMock(InlineByteBuddyMockMaker.java:56)
	at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:53)
	at org.mockito.internal.MockitoCore.mock(MockitoCore.java:96)
	at org.mockito.Mockito.mock(Mockito.java:1965)
	... 44 more
Caused by: java.lang.ClassCastException: Cannot cast [Ljava.lang.AutoCloseable; to java.lang.AutoCloseable
	at java.base/java.lang.Class.cast(Class.java:3605)
	at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:710)
	at java.base/java.lang.invoke.MethodHandleImpl$AsVarargsCollector.invokeWithArguments(MethodHandleImpl.java:578)
	at org.mockito.internal.util.reflection.InstrumentationMemberAccessor$Dispatcher$ByteBuddy$2DHh04hv.invokeWithArguments(Unknown Source)
	at org.mockito.internal.util.reflection.InstrumentationMemberAccessor.lambda$newInstance$0(InstrumentationMemberAccessor.java:191)
	at org.mockito.internal.util.reflection.InstrumentationMemberAccessor.newInstance(InstrumentationMemberAccessor.java:188)
	... 55 more

Changing the constructor param c to be AutoCloseable[] makes it work. Is it possible to invoke the constructor with varargs in this case?

[TimvdLippe]

I think the correct usage should be Mockito.withSettings().useConstructor("hi", 1, c), would that work? In case you want to specify multiple, it would become Mockito.withSettings().useConstructor("hi", 1, c1, c2).

[jeff303]

I think the correct usage should be Mockito.withSettings().useConstructor("hi", 1, c), would that work? In case you want to specify multiple, it would become Mockito.withSettings().useConstructor("hi", 1, c1, c2).

This: Mockito.mock(A.class, Mockito.withSettings().useConstructor("hi", 1, c))

fails with:

Caused by: org.mockito.creation.instance.InstantiationException: 
Unable to create instance of 'A'.
Please ensure that the target class has a constructor that matches these argument types: [java.lang.String, java.lang.Integer, MockitoTest$$Lambda$47/0x0000000800154840].
	... 44 more

I also tried with additional varargs values, and the exception thrown is similar.

[alvaro-martinez-hernandez]

@jeff303 The actual problem with your test is that the A class should be public, and its constructor as well. Otherwise Mockito can't find the constructor.

@TimvdLippe On the other hand, there is a "problem" with the withSettings().useConstructor() method: Mockito is unable to accept varargs without an array. Check this out:

@RunWith(MockitoJUnitRunner.class)
public class FakeClassTest extends TestBase {

    public static class A {

        public A(String a, int b, AutoCloseable... c) {
            System.out.println("Constructor called");
        }
    }

    @Test
    public void withArray() {

        AutoCloseable c = () -> {
            System.out.println("Closing");
        };
        A a = Mockito.mock(A.class, Mockito.withSettings().useConstructor("hi", 1, new AutoCloseable[]{c}));

    }

    @Test
    public void withoutArray() {

        AutoCloseable c = () -> {
            System.out.println("Closing");
        };
        A a = Mockito.mock(A.class, Mockito.withSettings().useConstructor("hi", 1, c));

    }
}

[big-andy-coates]

FYI @TimvdLippe, the test case in the description of this issue runs just find on the latest code (4.9.0).

Looks like this issue can be closed.

[TimvdLippe]

Thanks for confirming!

[yashmayya]

This issue occurs even with Mockito 4.11.0 (the latest 4.x version currently). I tried reproducing it with JDK 8, 11, 17 - the issue occurs on JDK 11 and JDK 17 but not on JDK 8. @TimvdLippe can this be re-opened?

[TimvdLippe]

@yashmayya Can you please open a PR to Mockito with the regression test so that we can confirm it still breaks and work towards fixing it?

[yashmayya]

@TimvdLippe here's the PR with the regression test - #3081. Looks like it's a fairly rarely encountered issue because it only occurs when using the inline mock maker with the member accessor module on Java 9 and newer.

[big-andy-coates]

Happy to take a look if we can merge in the test.

[yashmayya]

Is there a better way to configure the member accessor plugin? The draft PR I pushed out to demonstrate the bug will cause every test to use member-accessor-module which is probably not what we want.

[TimvdLippe]

We have a GitHub job matrix which should already be running at least that configuration. So maybe that file is not necessary and removing it will correctly fail only the job with the accessor.

[yashmayya]

Thanks Tim, that makes sense. I've removed that file.

[TimvdLippe]

Closing this per #3081 (comment)