Mocking static methods not working anymore since version 4.2.0 #2530

Hakky54 · 2022-01-01T20:58:55Z

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: Hakky54/sslcontext-kickstart#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,

The text was updated successfully, but these errors were encountered:

temp-droid · 2022-01-01T22:04:07Z

Hey @TimvdLippe , I think it is related to our recent changes here: #2506.

Not sure what is happening, but it is related to WrongTypeOfReturnValue kind of exception:

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

naninuneno · 2022-01-01T22:04:19Z

mockStatic()'s 2nd argument: the default answer when invoking static methods

try either dropping this argument:

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

or specify the default as the return type you need:

try (MockedStatic<FooUtils> ignored = Mockito.mockStatic(FooUtils.class, invocation -> "bar")) {
    String name = FooUtils.getName();
    assertThat(name).isEqualTo("bar");
}

Hakky54 · 2022-01-01T22:24:15Z

mockStatic()'s 2nd argument: the default answer when invoking static methods

Dropping the second parameter fixes the issue of the example with FooUtils, but in some cases I need to partially mock and therefor need the second parameter. I have couple of uses cases here:

I have copied one of the unit tests of the project below:

@Test
void getRootCaIfPossibleReturnsJdkTrustedCaCertificateWhenNoAuthorityInfoAccessExtensionIsPresent() {
    List<Certificate> certificates = CertificateUtils.getCertificate("https://www.reddit.com/")
            .get("https://www.reddit.com/");

    try (MockedStatic<CertificateUtils> certificateUtilsMockedStatic = mockStatic(CertificateUtils.class, invocation -> {
        Method method = invocation.getMethod();
        if ("getRootCaFromAuthorityInfoAccessExtensionIfPresent".equals(method.getName())) {
            return invocation.getMock();
        } else {
            return invocation.callRealMethod();
        }
    })) {
        certificateUtilsMockedStatic.when(() -> CertificateUtils.getRootCaFromAuthorityInfoAccessExtensionIfPresent(any(X509Certificate.class)))
                .thenReturn(Collections.emptyList());

        X509Certificate certificate = (X509Certificate) certificates.get(certificates.size() - 1);
        List<X509Certificate> rootCaCertificate = CertificateUtils.getRootCaIfPossible(certificate);
        assertThat(rootCaCertificate).isNotEmpty();

        certificateUtilsMockedStatic.verify(() -> CertificateUtils.getRootCaFromJdkTrustedCertificates(certificate), times(1));
    }
}

The error message for the above test is:

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

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

Any idea why the above one could be failing?

Hakky54 · 2022-01-01T22:39:46Z

I tried to add a cast to the returned object for the mocked one and then it passes. So I added:
return (List) invocation.getMock();

So the following test passes when having a explicite cast:

@Test
void getRootCaIfPossibleReturnsJdkTrustedCaCertificateWhenNoAuthorityInfoAccessExtensionIsPresent() {
    List<Certificate> certificates = CertificateUtils.getCertificate("https://www.reddit.com/")
            .get("https://www.reddit.com/");

    try (MockedStatic<CertificateUtils> certificateUtilsMockedStatic = mockStatic(CertificateUtils.class, invocation -> {
        Method method = invocation.getMethod();
        if ("getRootCaFromAuthorityInfoAccessExtensionIfPresent".equals(method.getName())) {
            return (List) invocation.getMock();
        } else {
            return invocation.callRealMethod();
        }
    })) {
        certificateUtilsMockedStatic.when(() -> CertificateUtils.getRootCaFromAuthorityInfoAccessExtensionIfPresent(any(X509Certificate.class)))
                .thenReturn(Collections.emptyList());

        X509Certificate certificate = (X509Certificate) certificates.get(certificates.size() - 1);
        List<X509Certificate> rootCaCertificate = CertificateUtils.getRootCaIfPossible(certificate);
        assertThat(rootCaCertificate).isNotEmpty();

        certificateUtilsMockedStatic.verify(() -> CertificateUtils.getRootCaFromJdkTrustedCertificates(certificate), times(1));
    }
}

https://github.com/Hakky54/sslcontext-kickstart/blob/19e8d74f0fb8d661693393354d4a1bba3471002f/sslcontext-kickstart/src/test/java/nl/altindag/ssl/util/CertificateUtilsShould.java#L212

temp-droid · 2022-01-01T22:40:47Z

           if ("getRootCaFromAuthorityInfoAccessExtensionIfPresent".equals(method.getName())) {
                return invocation.getMock();
            } else {
                return invocation.callRealMethod();
            }

invocation.getMock() returns a Class, could this be the class mentionned in Class cannot be returned by getRootCaFromAuthorityInfoAccessExtensionIfPresent()?

temp-droid · 2022-01-01T22:44:51Z

@Hakky54 , could you try to replace your code with:

if ("getRootCaFromAuthorityInfoAccessExtensionIfPresent".equals(method.getName())) {
    return Collections.emptyList();
}

The test passes with that change for me.

Hakky54 · 2022-01-01T23:26:06Z

Yes @temp-droid I can confirm that it is working like that.

I have rewritten the test like this and it passes:

@Test
void getRootCaIfPossibleReturnsJdkTrustedCaCertificateWhenNoAuthorityInfoAccessExtensionIsPresent() {
    List<Certificate> certificates = CertificateUtils.getCertificate("https://www.reddit.com/")
            .get("https://www.reddit.com/");

    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);
        List<X509Certificate> rootCaCertificate = CertificateUtils.getRootCaIfPossible(certificate);
        assertThat(rootCaCertificate).isNotEmpty();

        certificateUtilsMockedStatic.verify(() -> CertificateUtils.getRootCaFromJdkTrustedCertificates(certificate), times(1));
    }
}

This method resolves most of the issues I had.
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.

So basically what I wonder is should I rewrite my tests or do you think it is a bug and I should wait for a new mockito version? I have the feeling it

Looking at the PR of #2506 it gives me the idea that I was incorrectly using mockstatic and therefor with the latest version I am getting an exception right?

temp-droid · 2022-01-02T07:51:48Z

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 · 2022-01-02T08:25:20Z

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

Hakky54 closed this as completed Jan 2, 2022

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Mocking static methods not working anymore since version 4.2.0 #2530

Mocking static methods not working anymore since version 4.2.0 #2530

Hakky54 commented Jan 1, 2022 •

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temp-droid commented Jan 1, 2022

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Hakky54 commented Jan 1, 2022 •

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Hakky54 commented Jan 2, 2022

Mocking static methods not working anymore since version 4.2.0 #2530

Mocking static methods not working anymore since version 4.2.0 #2530

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Hakky54 commented Jan 1, 2022 • edited

temp-droid commented Jan 1, 2022

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