Junit5 mock a static method

From Mockito 3.4.0 (2020-07-10), it is possible to mock static methods out of the box even in JUnit 5, without any extension.

In the documentation, you can find an example: 48. Mocking static methods (since 3.4.0)

Important note: You need to use inline mock maker. So the dependency to use is not the core one:

        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-inline</artifactId>
            <version>3.4.6</version>
            <scope>test</scope>
        </dependency>

Example:
Class under test:

package teststatics;

public class FooWithStatics {
    public static Long noParameters() {
        return System.currentTimeMillis();
    }
    public static String oneParameter(String param1) {
        return param1.toUpperCase();
    }
}

Test class:

package teststatics;

import org.junit.jupiter.api.Test;
import org.mockito.MockedStatic;

import static org.junit.jupiter.api.Assertions.*;
import static org.mockito.Mockito.*;

public class FooWithStaticsTest {

    @Test
    void testStatic() {
        // Before mock scope, usual behavior.
        assertNotEquals(0L, FooWithStatics.noParameters());
        assertNotEquals("yyy", FooWithStatics.oneParameter("xxx"));

        // Mock scope
        try (MockedStatic mocked = mockStatic(FooWithStatics.class)) {

            // Mocking
            mocked.when(FooWithStatics::noParameters).thenReturn(0L);
            mocked.when(() -> FooWithStatics.oneParameter("xxx")).thenReturn("yyy");

            // Mocked behavior
            assertEquals(0L, FooWithStatics.noParameters());
            assertEquals("yyy", FooWithStatics.oneParameter("xxx"));

            // Verifying mocks.
            mocked.verify(times(1), FooWithStatics::noParameters);
            mocked.verify(times(1), () -> FooWithStatics.oneParameter("xxx"));
        }

        // After mock scope returns to usual behavior.
        assertNotEquals(0L, FooWithStatics.noParameters());
        assertNotEquals("yyy", FooWithStatics.oneParameter("xxx"));
    }
}