is MockitoAnnotations.initMocks implied?

Question

My tests seems to pass whether I use

@BeforeEach
void initMocks() {
    MockitoAnnotations.initMocks(this);
}

or not and I don't understand why since in the "Pivotal Certified Professional Core Spring 5 Developer" book I am reading an answer of a quizz says it's mandatory.

Here is the full code snippet concerned

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package com.apress.cems.mockito;

import com.apress.cems.dao.Storage;
import com.apress.cems.repos.StorageRepo;
import com.apress.cems.services.impl.SimpleStorageService;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;

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

import org.mockito.MockitoAnnotations;
import org.mockito.junit.jupiter.MockitoExtension;

import java.util.Optional;

import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.*;

/**
 * @author Iuliana Cosmina
 * @since 1.0
 * Description: new-style using Mockito mocks with JUnit 5
 */
@ExtendWith(MockitoExtension.class)
class SimpleStorageServiceTest3 {
    static final Long STORAGE_ID = 1L;

    @Mock //Creates mock instance of the field it annotates
    private StorageRepo mockRepo;

    @InjectMocks
    private SimpleStorageService storageService;

    @BeforeEach
    void initMocks() {
        MockitoAnnotations.initMocks(this);
    }

    @Test
    void findByIdPositive() {
        var storage = new Storage();
        storage.setId(STORAGE_ID);
        when(mockRepo.findById(any(Long.class))).thenReturn(Optional.of(storage));

        Storage result = storageService.findById(STORAGE_ID);

        verify(mockRepo, times(1)).findById(any(Long.class));
        assertAll(
                () -> assertNotNull(result),
                () -> assertEquals(storage.getId(), result.getId())
        );
    }
}

Removing the initMocks method doesn't change a thing, is that initialization implied in some sort of way by the rest of that code ?

Answer 1

MockitoAnnotations.initMocks(this); is only required if you are not using @ExtendWith(MockitoExtension.class). The extension does it for you each time a test method is invoked. See reference docs for the extension.

Answer 2

use MockitoAnnotations.openMocks(this); instead.