Mocking static methods (Mockito 3.4+) in JUnit - Test Execution Trace

Test Overview

This test verifies that a static method can be mocked using Mockito 3.4+ in a JUnit test. It checks that the mocked static method returns the expected value when called.

Test Code - JUnit with Mockito 3.4+

JUnit

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

class Utility {
    public static String getGreeting() {
        return "Hello, World!";
    }
}

public class StaticMockTest {
    @Test
    void testMockStaticMethod() {
        try (MockedStatic<Utility> mockedStatic = mockStatic(Utility.class)) {
            mockedStatic.when(Utility::getGreeting).thenReturn("Mocked Hello!");

            String result = Utility.getGreeting();

            assertEquals("Mocked Hello!", result);
        }
    }
}

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initialized	-	PASS
2	Mocks static method Utility.getGreeting using mockStatic	Static method getGreeting is mocked to return 'Mocked Hello!'	-	PASS
3	Calls Utility.getGreeting()	Static method call intercepted by mock	Check that returned value is 'Mocked Hello!'	PASS
4	Assert that result equals 'Mocked Hello!'	Assertion compares expected and actual values	assertEquals("Mocked Hello!", result)	PASS
5	Test ends and mock is closed	Static mocking context closed, original method restored	-	PASS

Failure Scenario

Failing Condition: Static method is not mocked correctly or mockStatic is not used

Execution Trace Quiz - 3 Questions

What does mockStatic(Utility.class) do in this test?

A It disables the Utility class

B It creates a mock instance of Utility class

C It creates a mock for all static methods of Utility class

D It calls the real static method

Key Result

Always use try-with-resources when mocking static methods with Mockito to ensure the mock is active only during the test and original behavior is restored after.