Mockito

Mockito是一個Java平臺的開源測試框架，在MIT許可證下發布。該框架允許在自動化單元測試中創建Test double對象（模擬對象），用於測試驅動開發（TDD）或行為驅動開發（BDD）。
該框架的名稱和圖標是對莫吉托（Mojito，一種飲料）的模仿。

**特點**
Mockito允許開發人員驗證被測系統（SUT）的行為，而無需事先建立期望。對於模擬對象，有人批評其測試代碼與被測系統的緊耦合。Mockito試圖通過取消期望規範，來擺脫“期望-運行-驗證”的模式。Mockito還提供了一些用於減少Boilerplate code的註解。

**起源**
Mockito是從擴展EasyMock的語法和功能開始的。

**例子**
下面是一個非耦合的Hello world程序；我們可以對它的某些部分進行單元測試，對其它部分使用模擬對象。
package org.examples;
import java.io.IOException;
public class HelloApplication {
public static interface Greeter {
String getGreeting(String subject);
String getIntroduction(String actor);
}

public static class HelloGreeter implements Greeter {
private String hello;
private String segmenter;

public HelloGreeter(String hello, String segmenter) {
this.hello = hello;
this.segmenter = segmenter;
}
public String getGreeting(String subject) {
return hello + " " + subject; 
}
public String getIntroduction(String actor) {
return actor+segmenter;
}
}

public static interface HelloActable {
void sayHello(String actor, String subject) throws IOException;
}

public static class HelloAction implements HelloActable {
private Greeter helloGreeter;
private Appendable helloWriter;
public HelloAction(Greeter helloGreeter, Appendable helloWriter) {
super();
this.helloGreeter = helloGreeter;
this.helloWriter = helloWriter;
}
public void sayHello(String actor, String subject) throws IOException { 
helloWriter.append(helloGreeter.getIntroduction(actor)).append(helloGreeter.getGreeting(subject));
}
}
public static void main(String... args) throws IOException {
new HelloAction(new HelloGreeter("hello", ": "), System.out).sayHello("application", "world");
}
}
啟動HelloApplication後，結果如下：
application: hello world
HelloActable組件的單元測試可能如下：
package org.examples;
import static org.mockito.Matchers.any;
import static org.mockito.Matchers.eq;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import org.junit.Before;
import org.junit.Test;
import org.examples.HelloApplication.HelloActable;
import org.examples.HelloApplication.HelloAction;
import org.examples.HelloApplication.Greeter;
public class HelloActionUnitTest {

Greeter helloGreeterMock;
Appendable helloWriterMock;
HelloActable helloAction;

@Before
public void setUp() {
helloGreeterMock = mock(Greeter.class);
helloWriterMock = mock(Appendable.class);
helloAction = new HelloAction(helloGreeterMock, helloWriterMock);
}

@Test
public void testSayHello() throws Exception {
when(helloWriterMock.append(any(String.class))).thenReturn(helloWriterMock);
when(helloGreeterMock.getIntroduction(eq("unitTest"))).thenReturn("unitTest : ");
when(helloGreeterMock.getGreeting(eq("world"))).thenReturn("hi world");

helloAction.sayHello("unitTest", "world");

verify(helloGreeterMock).getIntroduction(eq("unitTest"));
verify(helloGreeterMock).getGreeting(eq("world"));
verify(helloWriterMock, times(2)).append(any(String.class));
verify(helloWriterMock, times(1)).append(eq("unitTest : "));
verify(helloWriterMock, times(1)).append(eq("hi world"));
}
}
它為Greeter和Appendable接口使用了模擬對象，並隱式假設了下一個用例：
unitTest : hi world
用於測試Greeter與HelloActable聯合在一起的集成測試代碼可能如下：
package org.examples;
import static org.mockito.Matchers.any;
import static org.mockito.Matchers.eq;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import org.junit.Before;
import org.junit.Test;
import org.examples.HelloApplication.HelloActable;
import org.examples.HelloApplication.HelloAction;
import org.examples.HelloApplication.Greeter;
import org.examples.HelloApplication.HelloGreeter;
public class HelloActionIntegrationTest {
HelloActable helloAction;
Greeter helloGreeter;
Appendable helloWriterMock;

@Before
public void setUp() {
helloGreeter = new HelloGreeter("welcome", " says ");
helloWriterMock = mock(Appendable.class);
helloAction = new HelloAction(helloGreeter, helloWriterMock);
}

@Test
public void testSayHello() throws Exception {
when(helloWriterMock.append(any(String.class))).thenReturn(helloWriterMock);
helloAction.sayHello("integrationTest", "universe");
verify(helloWriterMock, times(2)).append(any(String.class));
verify(helloWriterMock, times(1)).append(eq("integrationTest says "));
verify(helloWriterMock, times(1)).append(eq("welcome universe"));
}
}
它僅使用模擬對象代替Appendable接口，而使用其它（HelloActable和Greeter）接口的真實實現，並隱式假設了下一個用例：
integrationTest says welcome universe
從HelloActionUnitTest和HelloActionIntegrationTest這兩個類的import語句可以看出，需要在Classpath中加入一些Mockito和JUnit的包才能編譯和運行測試類。

**參見**
 行為驅動開發- List of unit testing frameworks- 軟件測試

**參考資料**

**外部鏈接**
  http://mockito.org/