Mockito

Mockito是一个Java平台的开源测试框架，在MIT许可证下发布。该框架允许在自动化单元测试中创建Test double对象（模拟对象），用于测试驱动开发（TDD）或行为驱动开发（BDD）。
该框架的名称和图标是对莫吉托（Mojito，一种饮料）的模仿。

**特点**
Mockito允许开发人员验证被测系统（SUT）的行为，而无需事先建立期望。对于模拟对象，有人批评其测试代码与被测系统的紧耦合。Mockito试图通过取消期望规范，来摆脱“期望-运行-验证”的模式。Mockito还提供了一些用于减少Boilerplate code的注解。

**起源**
Mockito是从扩展EasyMock的语法和功能开始的。

**例子**
下面是一个非耦合的Hello world程序；我们可以对它的某些部分进行单元测试，对其它部分使用模拟对象。
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");
}
}
启动HelloApplication后，结果如下：
application: hello world
HelloActable组件的单元测试可能如下：
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"));
}
}
它为Greeter和Appendable接口使用了模拟对象，并隐式假设了下一个用例：
unitTest : hi world
用于测试Greeter与HelloActable联合在一起的集成测试代码可能如下：
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"));
}
}
它仅使用模拟对象代替Appendable接口，而使用其它（HelloActable和Greeter）接口的真实实现，并隐式假设了下一个用例：
integrationTest says welcome universe
从HelloActionUnitTest和HelloActionIntegrationTest这两个类的import语句可以看出，需要在Classpath中加入一些Mockito和JUnit的包才能编译和运行测试类。

**参见**
 行为驱动开发- List of unit testing frameworks- 软件测试

**参考资料**

**外部链接**
  http://mockito.org/