mockStatic of enum class is unstable - impacted by earlier use of the class (unrelated to mockStatic)

OS: Windows 10 Mockito: 3.7.0 JUnit5: 5.7.0 Java: 8 (8u202)

We have two tests. A and B. When run in the order [B, A] they pass. When run in the order [A, B] B fails. Failure is related to “switch” java statement with enum usage.

package com;

import org.junit.jupiter.api.MethodOrderer;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestMethodOrder;
import org.mockito.MockedStatic;
import org.springframework.test.util.ReflectionTestUtils;

import static com.MyEnum.A_VALUE;
import static com.MyEnum.B_VALUE;
import static com.MyEnum.C_VALUE;
import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.mockStatic;
import static org.mockito.Mockito.when;

@TestMethodOrder(MethodOrderer.MethodName.class)
class MyFactoryClassWithEnumTest {
    @Test
    void aTest() {
        MyFactoryClass factory = MyFactoryClass.create();

        assertThat(factory.valuesVisible()).isEqualTo(new MyEnum[] {
                A_VALUE,
                B_VALUE,
                C_VALUE
        });
        factory.switchEval(A_VALUE);
    }

    @Test
    void bTest() {
        MyEnum mockInstance = mock(MyEnum.class);
        when(mockInstance.ordinal()).thenReturn(MyEnum.values().length);
        ReflectionTestUtils.setField(mockInstance, "ordinal", MyEnum.values().length);

        try (MockedStatic<MyEnum> mockedDropType = mockStatic(MyEnum.class)) {
            mockedDropType.when(MyEnum::values).thenReturn(new MyEnum[]{
                    A_VALUE,
                    B_VALUE,
                    C_VALUE,
                    mockInstance
            });

            MyFactoryClass factory = MyFactoryClass.create();
            assertThat(factory.valuesVisible()).isEqualTo(new MyEnum[] {
                    A_VALUE,
                    B_VALUE,
                    C_VALUE,
                    mockInstance});
            factory.switchEval(mockInstance);
        }
    }
}

While classes are as simple as possible:

package com;

public enum MyEnum {
    A_VALUE,
    B_VALUE,
    C_VALUE
}

package com;

import lombok.AllArgsConstructor;

@AllArgsConstructor(staticName = "create")
public class MyFactoryClass {
    public void switchEval(MyEnum myEnum) {
        switch (myEnum) {
            default:
                System.out.println("DONE!");
        }
    }

    public MyEnum[] valuesVisible() {
        return MyEnum.values();
    }
}

MyFactoryClass is the class that should return in (here absent) method “of” appropriate object related to enum value. We want to test “default” scenario (if someone would be so nice to “override” our enum by his own enum by injecting it “earlier” in the classpath, or just when there’s an incompatibility somewhere along the line).

Obviously if there’s a better way to test such a scenario, we could change our approach accordingly.

[GregoryBevan]

I encountered the samed problem while mocking an Enum and found a workaround by moving the test that contains the MockedStatic call in an inner static class. This cause isolation of the test and doesn’t interfere with other tests.

Not a solution, just a workaround…

[roli2otlet]

Still struggling with the same issue. Inner static class was not helping at all to us unfortunately.