编程过程可以抽象为expect-run-verify，而在Java中我们常用单元测试来保证程序运行结果符合我们的预期。
Mockito可以实现：
- 在得到程序输出结果后，验证结果是否符合预期；
- 在其依赖方法还没有编写完成时，mock接口的执行结果。
mock
- 通过when(...).then(...)指定具体行为动作的mock结果；
- 可通过如下方式自定义响应：
when(mock.someMethod(anyString())).thenAnswer(
new Answer() {
public Object answer(InvocationOnMock invocation) {
Object[] args = invocation.getArguments();
Object mock = invocation.getMock();
return "called with arguments: " + Arrays.toString(args);
}
});
//Following prints "called with arguments: [foo]"
System.out.println(mock.someMethod("foo"));
import static org.mockito.Mockito.*;
// 通过mock方法创建一个mock类，该实例的所有调用返回的都是mock值
List mockedList = mock(List.class);
// 使用mock实例，不会抛出任何非检查型异常
mockedList.add("one");
mockedList.clear();
// 验证某方法是否执行过
verify(mockedList).add("one");
verify(mockedList).clear();
//定义一个stub存根，mock方法执行返回结果
when(mockedList.get(0)).thenReturn("first");
// 命中stub，符合上面定义的mock条件，返回mock结果
System.out.println(mockedList.get(0));
// 因为get(999)未命中stub，故返回null
System.out.println(mockedList.get(999));
测试输出结果如下：
mock测试结果
@mock
public class ArticleManagerTest extends SampleBaseTestCase {
@Mock private ArticleCalculator calculator;
@Mock(name = "database") private ArticleDatabase dbMock;
@Mock(answer = RETURNS_MOCKS) private UserProvider userProvider;
@Mock(extraInterfaces = {Queue.class, Observer.class}) private articleMonitor;
private ArticleManager manager;
@Before public void setup() {
manager = new ArticleManager(userProvider, database, calculator, articleMonitor);
}
}
public class SampleBaseTestCase {
@Before public void initMocks() {
//MockitoAnnotations.initMocks(this)必须在test执行前调用
MockitoAnnotations.initMocks(this);
}
}
spy
- mock代理部分指定的方法，其余方法都执行真实的方法动作。
List list = new LinkedList();
List spy = spy(list);
//可以选择性stub部分方法，其余未被代理的方法会真实执行
when(spy.size()).thenReturn(100);
//真实调用执行
spy.add("one");
spy.add("two");
//打印第一个元素
System.out.println(spy.get(0));
//size() 方法被mock代理了，返回设定值：100
System.out.println(spy.size());
//验证
verify(spy).add("one");
verify(spy).add("two");
测试输出结果如下：
spy测试结果
@spy
public class Test{
//Instance for spying is created by calling constructor explicitly:
@Spy Foo spyOnFoo = new Foo("argument");
//Instance for spying is created by mockito via reflection (only default constructors supported):
@Spy Bar spyOnBar;
@Before
public void init(){
MockitoAnnotations.initMocks(this);
}
...
}
/****************等同于*********/
Foo spyOnFoo = Mockito.spy(new Foo("argument"));
Bar spyOnBar = Mockito.spy(new Bar());
verify
- 验证执行方法是否被调用执行指定的次数
List<String> mockedList = mock(List.class);
//using mock
mockedList.add("once");
mockedList.add("twice");
mockedList.add("twice");
mockedList.add("three times");
mockedList.add("three times");
mockedList.add("three times");
//following two verifications work exactly the same - times(1) is used by default
verify(mockedList).add("once");
verify(mockedList, times(1)).add("once");
//exact number of invocations verification
verify(mockedList, times(2)).add("twice");
verify(mockedList, times(3)).add("three times");
//verification using never(). never() is an alias to times(0)
verify(mockedList, never()).add("never happened");
//verification using atLeast()/atMost()
verify(mockedList, atLeastOnce()).add("three times");
verify(mockedList, atLeast(2)).add("three times");
verify(mockedList, atMost(5)).add("three times");
