其他 mock 框架：powermock、easymock、jmock

mockito 官網：https://site.mockito.org

mockito 是一個單元測試框架。

Mockito 快速入門

下面來演示 Mockito 的入門案例。

包結構如下：

代碼如下：

實體類 Account.java：

public class Account { }

dao 層 AccountDao.java，該類中有一個接口，并且模擬數據庫宕機的情況：

public class AccountDao {public Account findAccount(String username, String password) {throw new UnsupportedOperationException(); // 模擬數據庫宕機情況}}

controller 層 AccountLoginController.java，該類中有一個接口：

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"; // 模擬返回登錄頁面} else {return "/index"; // 模擬登錄成功}} catch (Exception e) {return "/505"; // 模擬出錯情況}}}

此時 controller 層的接口 login() 已經定義好了，現在要對其進行單元測試，但沒有此時這個程序的環境中沒有 servlet 容器，也沒有數據庫，如何進行測試？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進行單元測試，記得加上這個注解 public class AccountLoginControllerTest {private AccountDao accountDao;private HttpServletRequest request;private AccountLoginController accountLoginController;// 每次測試開始前都會調用該方法，初始化上面定義的變量@Beforepublic void setUp() {this.accountDao = Mockito.mock(AccountDao.class); // 創建一個AccountDao的“替身”this.request = Mockito.mock(HttpServletRequest.class); // 創建一個HttpServletRequest的“替身”this.accountLoginController = new AccountLoginController(accountDao);}// 測試返回"/index"的情況@Testpublic void testLoginSuccess() {Account account = new Account();// 意思是：當調用request.getParameter("username")時，讓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);// 通過斷言來驗證結果assertThat(accountLoginController.login(request), equalTo("/index"));}// 測試返回"/login"的情況@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"));}// 測試返回"/505"的情況@Testpublic void testLogin505() {when(request.getParameter("username")).thenReturn("john");when(request.getParameter("password")).thenReturn("123456");when(accountDao.findAccount(anyString(), anyString())).thenThrow(UnsupportedOperationException.class); // 注意這調的是thenThrow()assertThat(accountLoginController.login(request), equalTo("/505"));}}

三種不同的 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);}}

打印結果：

null

如果不希望 account 為 null，可以將代碼修改如下：

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

此時打印結果：

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);}}

打印結果：

null

同樣，若不想 account 為 null，可按如下編碼：

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);}}

打印結果：

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);}}

打印結果：

null

深度 Mock（Deep Mock）

下面的例子中使用 @Mock 注解來進行單元測試：

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(); // 此時會報空指針異常}}

此時 testDeepMock() 測試無法通過，會報空指針異常，因為 person 為 null。

為了改進這個問題，將單元測試定義如下：

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

此時可以通過測試，完整代碼如下：

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(); // 此時會報空指針異常}@Testpublic void testDeepMock2() {when(personService.get()).thenReturn(person);Person person = personService.get();person.foo();}}

對于上面代碼，可以通過 Deep Mock 方式進行代碼簡化。簡化后的代碼如下：

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) // 指定為Deep Mockprivate PersonService personService;@Beforepublic void init() {MockitoAnnotations.initMocks(this);}@Testpublic void testDeepMock() {personService.get().foo();}}

Mockito Stubbing 語法詳解

#未完待續

參考教程：汪文君Mockito實戰視頻

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