如何使方法返回传递给它的参数?

你可以在mockito中创建一个答案。假设我们有一个名为application的接口和一个方法myfunction。

public interface Application {
  public String myFunction(String abc);
}

下面是mockito答案的测试方法:

public void testMyFunction() throws Exception {
  Application mock = mock(Application.class);
  when(mock.myFunction(anyString())).thenAnswer(new Answer<String>() {
    @Override
    public String answer(InvocationOnMock invocation) throws Throwable {
      Object[] args = invocation.getArguments();
      return (String) args[0];
    }
  });

  assertEquals("someString",mock.myFunction("someString"));
  assertEquals("anotherString",mock.myFunction("anotherString"));
}

由于Mockito 1.95和Java 8,使用lambda函数有更简单的方法:

when(myMock.myFunction(anyString())).thenAnswer(i -> i.getArguments()[0]);

如果您有mockito 1.9.5或更高版本,则有一个新的静态方法可以使 Answer 反对你。你需要写些

import static org.mockito.Mockito.when;
import static org.mockito.AdditionalAnswers.returnsFirstArg;

when(myMock.myFunction(anyString())).then(returnsFirstArg());

或者

doAnswer(returnsFirstArg()).when(myMock).myFunction(anyString());

请注意 returnsFirstArg() 方法在 AdditionalAnswers 类,这是Mockito1.9.5的新特性;因此您将需要正确的静态导入。

使用Java 8,甚至可以用旧版本的Mockito创建单行答案:

when(myMock.myFunction(anyString()).then(i -> i.getArgumentAt(0, String.class));

当然,这不如使用 AdditionalAnswers 由大卫华莱士建议,但如果你想转换论点“在飞行中”可能是有用的。

我也有类似的问题。目标是模拟一个持久化对象并可以按其名称返回它们的服务。服务如下所示:

public class RoomService {
    public Room findByName(String roomName) {...}
    public void persist(Room room) {...}
}

服务模拟使用一个映射来存储房间实例。

RoomService roomService = mock(RoomService.class);
final Map<String, Room> roomMap = new HashMap<String, Room>();

// mock for method persist
doAnswer(new Answer<Void>() {
    @Override
    public Void answer(InvocationOnMock invocation) throws Throwable {
        Object[] arguments = invocation.getArguments();
        if (arguments != null && arguments.length > 0 && arguments[0] != null) {
            Room room = (Room) arguments[0];
            roomMap.put(room.getName(), room);
        }
        return null;
    }
}).when(roomService).persist(any(Room.class));

// mock for method findByName
when(roomService.findByName(anyString())).thenAnswer(new Answer<Room>() {
    @Override
    public Room answer(InvocationOnMock invocation) throws Throwable {
        Object[] arguments = invocation.getArguments();
        if (arguments != null && arguments.length > 0 && arguments[0] != null) {
            String key = (String) arguments[0];
            if (roomMap.containsKey(key)) {
                return roomMap.get(key);
            }
        }
        return null;
    }
});

我们现在可以在这个模型上运行测试了。例如:

String name = "room";
Room room = new Room(name);
roomService.persist(room);
assertThat(roomService.findByName(name), equalTo(room));
assertNull(roomService.findByName("none"));

用Java 8, Steve's answer 可以成为

public void testMyFunction() throws Exception {
    Application mock = mock(Application.class);
    when(mock.myFunction(anyString())).thenAnswer(
    invocation -> {
        Object[] args = invocation.getArguments();
        return args[0];
    });

    assertEquals("someString", mock.myFunction("someString"));
    assertEquals("anotherString", mock.myFunction("anotherString"));
}

编辑:更短:

public void testMyFunction() throws Exception {
    Application mock = mock(Application.class);
    when(mock.myFunction(anyString())).thenAnswer(
        invocation -> invocation.getArgument(0));

    assertEquals("someString", mock.myFunction("someString"));
    assertEquals("anotherString", mock.myFunction("anotherString"));
}

我使用了类似的方法(基本上是相同的方法)。有时,让模拟对象返回某些输入的预定义输出是很有用的。就像这样:

private Hashtable<InputObject,  OutputObject> table = new Hashtable<InputObject, OutputObject>();
table.put(input1, ouput1);
table.put(input2, ouput2);

...

when(mockObject.method(any(InputObject.class))).thenAnswer(
       new Answer<OutputObject>()
       {
           @Override
           public OutputObject answer(final InvocationOnMock invocation) throws Throwable
           {
               InputObject input = (InputObject) invocation.getArguments()[0];
               if (table.containsKey(input))
               {
                   return table.get(input);
               }
               else
               {
                   return null; // alternatively, you could throw an exception
               }
           }
       }
       );

您可能希望将verify()与ArgumentCaptor结合使用,以确保在测试中执行,并使用ArgumentCaptor计算参数:

ArgumentCaptor<String> argument = ArgumentCaptor.forClass(String.class);
verify(mock).myFunction(argument.capture());
assertEquals("the expected value here", argument.getValue());

显然可以通过argument.getValue()访问该参数的值,以便进一步操作/检查/whatever。

这是一个很老的问题,但我认为仍然相关。同样,接受的答案只适用于字符串。同时还有Mockito 2.1和一些导入已经改变,所以我想分享我目前的答案:

import static org.mockito.AdditionalAnswers.returnsFirstArg;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.when;

@Mock
private MyClass myClass;

// this will return anything you pass, but it's pretty unrealistic
when(myClass.myFunction(any())).then(returnsFirstArg());
// it is more "life-like" to accept only the right type
when(myClass.myFunction(any(ClassOfArgument.class))).then(returnsFirstArg());

myClass.myFunction看起来像:

public class MyClass {
    public ClassOfArgument myFunction(ClassOfArgument argument){
        return argument;
    }  
}