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第一行代码，静态导入

import static org.mockito.Mockito.*;

测试桩 (Stub)

常用的当在调用外部接口的时候可以使用测试桩返回固定的一些值

 //You can mock concrete classes, not only interfaces
 // 你可以mock具体的类型,不仅只是接口
 LinkedList mockedList = mock(LinkedList.class);

 //stubbing 测试桩
 when(mockedList.get(0)).thenReturn("first");
 when(mockedList.get(1)).thenThrow(new RuntimeException());

 //following prints "first" 输出“first”
 System.out.println(mockedList.get(0));

 //following throws runtime exception  抛出异常
 System.out.println(mockedList.get(1));

 //following prints "null" because get(999) was not stubbed
 // 因为get(999) 没有打桩，因此输出null
 System.out.println(mockedList.get(999));

mock 异常抛出

无返回值

doThrow(new RuntimeException()).when(mockedList).clear();

有返回值的

when(mockedList.get(anyInt())).thenThrow(new RuntimeException());

参数匹配器 (matchers)

当参数可能不确定的时候 anyInt() 来匹配

// 使用内置的anyInt()参数匹配器
 when(mockedList.get(anyInt())).thenReturn("element");

为连续的调用做测试桩 (stub)

List mockedList = mock(List.class);
when(mockedList.get(anyInt()))
            .thenThrow(new RuntimeException())
            .thenReturn("foo");
// First call: throws runtime exception:
// 第一次调用 : 抛出运行时异常
try {
     mockedList.get(2);
} catch (Exception e) {
     System.out.println("有异常");
}
// Second call: prints "foo"
// 第二次调用 : 输出"foo"
System.out.println(mockedList.get(3));
// Any consecutive call: prints "foo" as well (last stubbing wins).
// 后续调用 : 也是输出"foo"
System.out.println(mockedList.get(4));

简化写法

// 第一次调用时返回"one",第二次返回"two",第三次返回"three"
 when(mock.someMethod("some arg"))
   .thenReturn("one", "two", "three");

为回调写测试桩(有返回值)

 when(mock.someMethod(anyString())).thenAnswer(new Answer() {
     Object answer(InvocationOnMock invocation) {
         Object[] args = invocation.getArguments();
         Object mock = invocation.getMock();
         return "called with arguments: " + args;
     }
 });
 //Following prints "called with arguments: foo"
 // 输出 : "called with arguments: foo"
 System.out.println(mock.someMethod("foo"));

        List mockedList = mock(List.class);
        mockedList.add("haha");
        when(mockedList.get(anyInt())).thenAnswer(
            (invocation) -> {
                // 获取所有参数
                Object[] args = invocation.getArguments();
                // 获取第一个参数
                Object firstArgs = invocation.getArgument(0);
                return "called with arguments: " + firstArgs;
            });
        // 最后答应出 回调函数中的东西
        System.out.println(mockedList.get(2));

回调测试桩

这样写可能更好，注意这时候when监控的是 mockedList

        doAnswer(x->{
            System.out.println("clear");
            return null;
        }).when(mockedList).clear();
        mockedList.clear();

• doReturn(Object)
• doThrow(Throwable)
• doThrow(Class)
• doAnswer(Answer)
• doNothing()
• doCallRealMethod()

verify 验证你的程序

 verify(mockedList, atLeastOnce()).add("three times");

比如 至少被执行两次，如果只 add 一次就会报错

List mockedList = mock(List.class);
        mockedList.add("one");
        mockedList.add("one");
        verify(mockedList,atLeast(2)).add("one");