Error mocking final class with static method with JUnit 4.x and Mockito.

[abu0khalique]

Hi,

I am having challenges stubbing a final class with static method for kafka.admin;AdminUtils. So i wanted to make sure final class static method can be stubbed.

I have copied a class called

public final class AFinalClass {

    public static final String echoString(String s) {

        return s;

    }

}

and a test 

@PrepareForTest({AFinalClass.class})

public class AFinalClassTest {

    @Rule

    public MockitoRule mockitoRule = MockitoJUnit.rule();

    @Rule

    public PowerMockRule powerMockRule = new PowerMockRule();

    @Test

    public void mockFinalClassTest() {

        PowerMockito.mockStatic(AFinalClass.class);

        AFinalClass stub = mock(AFinalClass.class);

        final String testInput = "A test input";

        final String mockedResult = "Mocked final echo result - " + testInput;

        PowerMockito.when(stub.echoString(testInput)).thenReturn(mockedResult);

        // Assert the mocked result is returned from method call

        Assert.assertEquals(stub.echoString(testInput), mockedResult);

    }

}

but I get this error message

java.lang.IllegalArgumentException: Cannot subclass final class class org.song.example.AFinalClass

at org.mockito.cglib.proxy.Enhancer.generateClass(Enhancer.java:447)

at org.mockito.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)

at org.mockito.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:217)

at org.mockito.cglib.proxy.Enhancer.createHelper(Enhancer.java:378)

at org.mockito.cglib.proxy.Enhancer.createClass(Enhancer.java:318)

at org.powermock.api.mockito.repackaged.ClassImposterizer.createProxyClass(ClassImposterizer.java:124)

at org.powermock.api.mockito.repackaged.ClassImposterizer.imposterise(ClassImposterizer.java:58)

at org.powermock.api.mockito.internal.mockcreation.MockCreator.createMethodInvocationControl(MockCreator.java:122)

at org.powermock.api.mockito.internal.mockcreation.MockCreator.createMock(MockCreator.java:70)

at org.powermock.api.mockito.internal.mockcreation.MockCreator.mock(MockCreator.java:47)

at org.powermock.api.mockito.PowerMockito.mockStatic(PowerMockito.java:71)

at org.song.example.AFinalClassTest.mockFinalClassTest(AFinalClassTest.java:30)

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:46)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:43)

at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)

at org.mockito.internal.junit.JUnitRule$1.evaluate(JUnitRule.java:16)

at org.powermock.modules.junit4.rule.PowerMockStatement.evaluate(PowerMockRule.java:75)

at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:270)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:62)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:52)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)

at org.junit.runners.ParentRunner.run(ParentRunner.java:307)

at org.junit.runner.JUnitCore.run(JUnitCore.java:152)

at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)

at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)

at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)

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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

I am using

Java 1.8,  following gradle dependencies

    testCompile "junit:junit:4.11"

    testCompile 'org.hamcrest:hamcrest-core:1.3'

    testCompile 'org.hamcrest:hamcrest-library:1.3'

    testCompile 'com.github.stefanbirkner:system-rules:1.16.0'

    testCompile 'junit-addons:junit-addons:1.4'

    testCompile "org.mockito:mockito-all:2.0.2-beta"

    testCompile "org.powermock:powermock-module-junit4:1.6.5"

    testCompile "org.powermock:powermock-api-mockito:1.6.5"

    testCompile "org.powermock:powermock-module-junit4-rule-agent:1.6.5"

[Johan Haleby]

Hi,

It might be because you're using the JUnit rule which is (still) experimental. If possible I suggest that you use the PowerMockRunner.

Regards,

/Johan

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[abu0khalique]

Thanks it works without rules

@RunWith(PowerMockRunner.class)

@PrepareForTest({AFinalClass.class})

public class AFinalClassTest {

    //@Rule

    //public MockitoRule mockitoRule = MockitoJUnit.rule();

    //@Rule

    //public PowerMockRule powerMockRule = new PowerMockRule();

    @Test

    public void mockFinalClassTest() {

        PowerMockito.mockStatic(AFinalClass.class);

        final String testInput = "A test input";

        final String mockedResult = "Mocked final echo result - " + testInput;

        PowerMockito.when(AFinalClass.echoString(testInput)).thenReturn(mockedResult);

        // Assert the mocked result is returned from method call

        Assert.assertEquals(AFinalClass.echoString(testInput), mockedResult);