Verification times (times, never, atLeast) in JUnit - Test Execution Trace

Test Overview

This test verifies how many times a mock method is called using JUnit with Mockito. It checks that a method is called exactly twice, never called with a certain argument, and called at least once.

Test Code - JUnit with Mockito

JUnit

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

public class VerificationTimesTest {

    interface Service {
        void performAction(String input);
    }

    @Test
    void testVerificationTimes() {
        Service mockService = mock(Service.class);

        // Call performAction twice with "hello"
        mockService.performAction("hello");
        mockService.performAction("hello");

        // Call performAction once with "world"
        mockService.performAction("world");

        // Verify performAction called exactly twice with "hello"
        verify(mockService, times(2)).performAction("hello");

        // Verify performAction never called with "test"
        verify(mockService, never()).performAction("test");

        // Verify performAction called at least once with "world"
        verify(mockService, atLeast(1)).performAction("world");
    }
}

Execution Trace - 7 Steps

Step	Action	System State	Assertion	Result
1	Test starts	JUnit test runner initialized, Mockito mock created for Service interface	-	PASS
2	Calls mockService.performAction("hello") twice	Mock records two calls with argument "hello"	-	PASS
3	Calls mockService.performAction("world") once	Mock records one call with argument "world"	-	PASS
4	Verifies performAction called exactly twice with "hello" using verify(mockService, times(2))	Mockito checks recorded calls for "hello" argument	Exactly 2 calls with "hello" found	PASS
5	Verifies performAction never called with "test" using verify(mockService, never())	Mockito checks recorded calls for "test" argument	No calls with "test" found	PASS
6	Verifies performAction called at least once with "world" using verify(mockService, atLeast(1))	Mockito checks recorded calls for "world" argument	At least 1 call with "world" found	PASS
7	Test ends successfully	All verifications passed	-	PASS

Failure Scenario

Failing Condition: If performAction is called fewer or more times than expected for a verification, or called with unexpected arguments

Execution Trace Quiz - 3 Questions

What does verify(mockService, never()).performAction("test") check?

A That performAction was called exactly once with argument "test"

B That performAction was called at least once with argument "test"

C That performAction was never called with argument "test"

D That performAction was called twice with argument "test"

Key Result

Use verification times to precisely check how many times a mock method is called, which helps catch unexpected behavior in your code.