无法使用PowerMockRunner运行JUnit测试

Question

I have a Gradle based Java project were I now want to mock a private method using PowerMock. The problem is that I am not able to use the PowerMockRunner as I always get the following exception when I add the @RunWith(org.powermock.modules.junit4.PowerMockRunner.class) annotation.

Error:

org.powermock.reflect.exceptions.FieldNotFoundException: Field 'fTestClass' was not found in class org.junit.internal.runners.MethodValidator.
at org.powermock.reflect.internal.WhiteboxImpl.getInternalState(WhiteboxImpl.java:581)
at org.powermock.reflect.Whitebox.getInternalState(Whitebox.java:308)
at org.powermock.modules.junit4.internal.impl.testcaseworkaround.PowerMockJUnit4MethodValidator.validate TestMethods(PowerMockJUnit4MethodValidator.java:79)
at org.powermock.modules.junit4.internal.impl.testcaseworkaround.PowerMockJUnit4MethodValidator.validate InstanceMethods(PowerMockJUnit4MethodValidator.java:49)
at org.junit.internal.runners.MethodValidator.validateMethodsForDefaultRunner(MethodValidator.java:51)
at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.validate(PowerMockJUnit44RunnerDelegateImpl.java:108)
...

This are my test dependencies:

testCompile 'junit:junit:4.+',
            'org.powermock:powermock-core:1.5.6',
            'org.powermock:powermock-module-junit4:1.5.6',
            'org.powermock:powermock-api-mockito:1.5.6'

The test itself fails also when completely empty (initialization error):

@RunWith(PowerMockRunner.class)
public class SomeTest {
    @Test
    public void testSomething() {
    }
}

Any ideas what might be wrong? Other tests using PowerMock are working fine (none of them uses the PowerMockRunner).

Greetings and thanks for any help! Ben

Answer 1

This is a bug that occurs when you use JUnit 4.12 and PowerMock < 1.6.1. The problem is solved in PowerMock 1.6.1. Please update your dependencies accordingly

testCompile 'junit:junit:4.12',
            'org.powermock:powermock-core:1.6.1',
            'org.powermock:powermock-module-junit4:1.6.1',
            'org.powermock:powermock-api-mockito:1.6.1'

If you cannot upgrade PowerMock then you can use JUnit 4.11.

testCompile 'junit:junit:4.11',
            'org.powermock:powermock-core:1.5.6',
            'org.powermock:powermock-module-junit4:1.5.6',
            'org.powermock:powermock-api-mockito:1.5.6'

Could you please add further lines of the stacktrace, which uncover more details about the problem.

Answer 2

There has been a bug logged against PowerMock: https://code.google.com/p/powermock/issues/detail?id=531

It appears that JUnit changed some of its internal field names that PowerMock was accessing via reflection, thus breaking the ability for PowerMock to properly inject itself.

Answer 3

Check what Stefan said, and above that you also need to add

@PrepareForTest({<The class/es you are Mocking>, ...})

without the prepare for test, PowerMockRunner won't know which class is mocked.