Mockito 实战总结笔记

其他 mock 框架：powermock、easymock、jmock

mockito 官网：https://site.mockito.org

mockito 是一个单元测试框架。

Mockito 快速入门

下面来演示 Mockito 的入门案例。

包结构如下：

代码如下：

实体类 Account.java：

public class Account {}

dao 层 AccountDao.java，该类中有一个接口，并且模拟数据库宕机的情况：

public class AccountDao {public Account findAccount(String username, String password) {throw new UnsupportedOperationException(); // 模拟数据库宕机情况}}

controller 层 AccountLoginController.java，该类中有一个接口：

public class AccountLoginController {private final AccountDao accountDao;public AccountLoginController(AccountDao accountDao) {this.accountDao = accountDao;}public String login(HttpServletRequest request) {final String userName = request.getParameter("username");final String password = request.getParameter("password");try {Account account = accountDao.findAccount(userName, password);if (account == null) {return "/login"; // 模拟返回登录页面} else {return "/index"; // 模拟登录成功}} catch (Exception e) {return "/505"; // 模拟出错情况}}}

此时 controller 层的接口 login() 已经定义好了，现在要对其进行单元测试，但没有此时这个程序的环境中没有 servlet 容器，也没有数据库，如何进行测试？用 mockito ！

AccountLoginControllerTest.java：

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.mockito.runners.MockitoJUnitRunner;import javax.servlet.http.HttpServletRequest;import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.mockito.Matchers.anyString;
import static org.mockito.Mockito.when;@RunWith(MockitoJUnitRunner.class) // 使用mockito进行单元测试，记得加上这个注解
public class AccountLoginControllerTest {private AccountDao accountDao;private HttpServletRequest request;private AccountLoginController accountLoginController;// 每次测试开始前都会调用该方法，初始化上面定义的变量@Beforepublic void setUp() {this.accountDao = Mockito.mock(AccountDao.class); // 创建一个AccountDao的“替身”this.request = Mockito.mock(HttpServletRequest.class); // 创建一个HttpServletRequest的“替身”this.accountLoginController = new AccountLoginController(accountDao);}// 测试返回"/index"的情况@Testpublic void testLoginSuccess() {Account account = new Account();// 意思是：当调用request.getParameter("username")时，让request.getParameter("username")返回"john"when(request.getParameter("username")).thenReturn("john"); when(request.getParameter("password")).thenReturn("123456");// anyString()：任意字符串when(accountDao.findAccount(anyString(), anyString())).thenReturn(account);// 通过断言来验证结果assertThat(accountLoginController.login(request), equalTo("/index"));}// 测试返回"/login"的情况@Testpublic void testLoginFailure() {when(request.getParameter("username")).thenReturn("john");when(request.getParameter("password")).thenReturn("123456");when(accountDao.findAccount(anyString(), anyString())).thenReturn(null);assertThat(accountLoginController.login(request), equalTo("/login"));}// 测试返回"/505"的情况@Testpublic void testLogin505() {when(request.getParameter("username")).thenReturn("john");when(request.getParameter("password")).thenReturn("123456");when(accountDao.findAccount(anyString(), anyString())).thenThrow(UnsupportedOperationException.class); // 注意这调的是thenThrow()assertThat(accountLoginController.login(request), equalTo("/505"));}}

三种不同的 mock 方式

方式一：使用 @RunWith 注解

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.runners.MockitoJUnitRunner;import static org.mockito.Mockito.mock;@RunWith(MockitoJUnitRunner.class)
public class MockByRunnerTest {@Testpublic void testMock() {AccountDao accountDao = mock(AccountDao.class);Account account = accountDao.findAccount("x", "x");System.out.println(account);}}

打印结果：

null

如果不希望 account 为 null，可以将代码修改如下：

@Test
public void testMock() {AccountDao accountDao = mock(AccountDao.class, Mockito.RETURNS_SMART_NULLS);Account account = accountDao.findAccount("x", "x");System.out.println(account);
}

此时打印结果：

SmartNull returned by this unstubbed method call on a mock:
accountDao.findAccount("x", "x");

方式二：@Mock 注解

import org.junit.Before;
import org.junit.Test;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;public class MockByAnnotationTest {@Beforepublic void init() {MockitoAnnotations.initMocks(this);}@Mockprivate AccountDao accountDao;@Testpublic void testMock() {Account account = accountDao.findAccount("x", "x");System.out.println(account);}}

打印结果：

null

同样，若不想 account 为 null，可按如下编码：

import org.junit.Before;
import org.junit.Test;
import org.mockito.Answers;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;public class MockByAnnotationTest {@Beforepublic void init() {MockitoAnnotations.initMocks(this);}@Mock(answer = Answers.RETURNS_SMART_NULLS)private AccountDao accountDao;@Testpublic void testMock() {Account account = accountDao.findAccount("x", "x");System.out.println(account);}}

打印结果：

SmartNull returned by this unstubbed method call on a mock:
accountDao.findAccount("x", "x");

方式三：@Rule 注解

import org.junit.Rule;
import org.junit.Test;
import org.mockito.junit.MockitoJUnit;
import org.mockito.junit.MockitoRule;import static org.mockito.Mockito.mock;public class MockByRuleTest {@Rulepublic MockitoRule mockitoRule = MockitoJUnit.rule();@Testpublic void testMock() {AccountDao accountDao = mock(AccountDao.class);Account account = accountDao.findAccount("x", "x");System.out.println(account);}}

打印结果：

null

深度 Mock（Deep Mock）

下面的例子中使用 @Mock 注解来进行单元测试：

import org.junit.Before;
import org.junit.Test;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;import static org.mockito.Mockito.when;public class DeepMockTest {@Mockprivate PersonService personService;@Mockprivate Person person;@Beforepublic void init() {MockitoAnnotations.initMocks(this);}@Testpublic void testDeepMock() {Person person = personService.get();person.foo(); // 此时会报空指针异常}}

此时 testDeepMock() 测试无法通过，会报空指针异常，因为 person 为 null。

为了改进这个问题，将单元测试定义如下：

@Test
public void testDeepMock2() {when(personService.get()).thenReturn(person);Person person = personService.get();person.foo();
}

此时可以通过测试，完整代码如下：

import org.junit.Before;
import org.junit.Test;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;import static org.mockito.Mockito.when;public class DeepMockTest {@Mockprivate PersonService personService;@Mockprivate Person person;@Beforepublic void init() {MockitoAnnotations.initMocks(this);}@Testpublic void testDeepMock() {Person person = personService.get();person.foo(); // 此时会报空指针异常}@Testpublic void testDeepMock2() {when(personService.get()).thenReturn(person);Person person = personService.get();person.foo();}}

对于上面代码，可以通过 Deep Mock 方式进行代码简化。简化后的代码如下：

import org.junit.Before;
import org.junit.Test;
import org.mockito.Answers;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;public class DeepMockTest {@Mock(answer = Answers.RETURNS_DEEP_STUBS) // 指定为Deep Mockprivate PersonService personService;@Beforepublic void init() {MockitoAnnotations.initMocks(this);}@Testpublic void testDeepMock() {personService.get().foo();}}

Mockito Stubbing 语法详解

#未完待续

参考教程：汪文君Mockito实战视频