Mocking static methods not working anymore since version 4.2.0

Hello, recently I tried to upgrade to the latest Mockito version from 4.1.0 to 4.2.0 which resulted in a failing build. I noticed that the unit tests which used mockstatic was not passing anymore. I can share a simple code snippet which worked and does not work anymore with the latest version:

FooUtils

public final class FooUtils {

    private FooUtils() {}

    public static String getName() {
        return "Foo";
    }

}

Unit Test

import org.junit.jupiter.api.Test;
import org.mockito.MockedStatic;
import org.mockito.Mockito;
import org.mockito.invocation.InvocationOnMock;

import static org.assertj.core.api.Assertions.assertThat;

class FooTest {

    @Test
    void getName() {
        try (MockedStatic<FooUtils> mockedFooUtils = Mockito.mockStatic(FooUtils.class, InvocationOnMock::getMock)) {
            mockedFooUtils.when(FooUtils::getName).thenReturn("bar");
            String name = FooUtils.getName();
            assertThat(name).isEqualTo("bar");
        }
    }

}

The test fails and I am getting the following error:

org.mockito.exceptions.misusing.WrongTypeOfReturnValue: 
Default answer returned a result with the wrong type:
Class cannot be returned by getName()
getName() should return String

The default answer of FooUtils.class that was configured on the mock is probably incorrectly implemented.

See also this project where I use mockstatic: https://github.com/Hakky54/sslcontext-kickstart The master branch is with mockito 4.1.0 which passes however this pull request where the latest version is being used fails: https://github.com/Hakky54/sslcontext-kickstart/pull/135

I am using Java 8, 11 and 17 and it fails on all of them. I am using mockito-junit-jupiter. Any idea what could be the cause? Do you think I am using the mockstatic wrong or do I need additional configuration for the latest version?

Looking forward to hear from you guys soon.

Hakan,

[temp-droid]

Hey @Hakky54 ,

Do you think I have incorrectly used mocking with mockstatic or do you think there is a bug in the latest version? I never had this issue with the initial test until the latest version.

It looks to me your implementation was wrong (because you don’t return a List), and your attempt to fix it (casting the invocation.getMock() to a List) avoids the type verification that would throw an error.

And because you mock it again after (certificateUtilsMockedStatic.when(() -> CertificateUtils.getRootCaFromAuthorityInfoAccessExtensionIfPresent(any(X509Certificate.class))) .thenReturn(Collections.emptyList());), it overrides your previous configuration and makes the test pass. If you remove the certificateUtilsMockedStatic.when( part, your test should still pass. But in that case your first mock should return a valid List, otherwise you will face java.lang.ClassCastException: class java.lang.Class cannot be cast to class java.util.List.

In the end, you could use:

        try (MockedStatic<CertificateUtils> certificateUtilsMockedStatic = mockStatic(CertificateUtils.class, invocation -> {
            Method method = invocation.getMethod();
            if ("getRootCaFromAuthorityInfoAccessExtensionIfPresent".equals(method.getName())) {
                return Collections.emptyList();
            } else {
                return invocation.callRealMethod();
            }
        })) {

            X509Certificate certificate = (X509Certificate) certificates.get(certificates.size() - 1);

[Hakky54]

Thank you for taking your time to look at this issue, and yes I totally agree with you that my test setup was not correct and adjusting it from my side fixes all the failing tests. I think we can close this issue as it is not an issue