Unable to verify when spying on kotlin class

[MFAshby]

I have a test class with 2 tests (written in java). The tests are trying to verify the behaviour of the subject (written in kotlin) by spying on it.

Expected behaviour:
tests pass because the expected method call is made.

Actual behaviour:
The first test passes, and the second (identical) test receives an UnfinishedVerificationException

Compilable example here:
https://github.com/MFAshby/spying-problem-sample

Problematic code:
SomeClass.kt:

package org.example

open class SomeClass {
    fun doThing1() {
        doThing2()
    }

    fun doThing2() {
        println("Hey")
    }
}

SpyingProblemTest.java:

package org.example;


import org.junit.Test;

import static org.mockito.Mockito.*;

public class SpyingProblemTest {
    private SomeClass underTest = spy(new SomeClass());

    @Test
    public void cantVerifySpies() {

        // WHEN
        underTest.doThing1();

        // THEN
        verify(underTest, times(1)).doThing2();
    }

    @Test
    public void cantVerifySpies2() {

        // WHEN
        underTest.doThing1();

        // THEN
        verify(underTest, times(1)).doThing2();
    }
}

Test output:

Hey
Hey

org.mockito.exceptions.misusing.UnfinishedVerificationException: 
Missing method call for verify(mock) here:
-> at org.example.SpyingProblemTest.cantVerifySpies(SpyingProblemTest.java:18)

Example of correct verification:
    verify(mock).doSomething()

Also, this error might show up because you verify either of: final/private/equals()/hashCode() methods.
Those methods *cannot* be stubbed/verified.
Mocking methods declared on non-public parent classes is not supported.


	at org.example.SpyingProblemTest.<init>(SpyingProblemTest.java:9)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.junit.runners.BlockJUnit4ClassRunner.createTest(BlockJUnit4ClassRunner.java:217)
	at org.junit.runners.BlockJUnit4ClassRunner$1.runReflectiveCall(BlockJUnit4ClassRunner.java:266)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.BlockJUnit4ClassRunner.methodBlock(BlockJUnit4ClassRunner.java:263)
	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$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)


Process finished with exit code 255

I originally logged this with mockito-kotlin but I subsequently reproduced the issue without that library, so I think the problem is in mockito.

Interesting version numbers:

<kotlin.version>1.3.61</kotlin.version>
<junit.version>4.12</junit.version>
<mockito-core.version>3.0.0</mockito-core.version>

[bohsen]

@MFAshby You have to use open on doThing2() function too or use mockito-inline.

Sry for not getting back to you on the original issue. Totally forgot.

[bohsen]

This works:

open class SomeClass {
   fun doThing1() {
        doThing2()
    }

    open fun doThing2() {
        println("Hey")
    }
}

public class SpyingProblemTest {
    private SomeClass underTest = spy(new SomeClass());

    @Test
    public void cantVerifySpies() {

        // WHEN
        underTest.doThing1();

        // THEN
        verify(underTest, times(1)).doThing2();
    }

    @Test
    public void cantVerifySpies2() {

        // WHEN
        underTest.doThing2();

        // THEN
        verify(underTest, times(1)).doThing2();
    }
}

[bohsen]

Maybe change your dependency on mockito-core to mockito-inline.

Replace mockito-core with this in your pom:

<dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-inline</artifactId>
        <version>${mockito-inline.version}</version>
        <scope>test</scope>
</dependency>