Mockito中ArgumentCaptor的使用方法

Test Double (http://xunitpatterns.com/Test%20Double.html)中有Spy Pattern。

我们来看下如何使用ArgumentCaptor

@RunWith(MockitoJUnitRunner.class)
public class SeriousThingTest {
    @Mock
    private Logger spyLogger;

    @Captor
    private ArgumentCaptor<LogRecord> logRecordArgumentCaptor;

    @Test
    public void should_log_serious_thing() {
        new People(spyLogger).doSomethingSerious();

        verify(spyLogger).log(logRecordArgumentCaptor.capture());

        assertThat(logRecordArgumentCaptor.getValue().getLevel(), is(Level.WARNING));
        assertThat(logRecordArgumentCaptor.getValue().getMessage(), is("someone is doing something very dangerous"));
    }
}

class People {
    private final Logger seriousLogger;

    public People(Logger seriousLogger) {
        this.seriousLogger = seriousLogger;
    }

    public void doSomethingSerious() {
        seriousLogger.log(new LogRecord(Level.WARNING, "someone is doing something very dangerous"));
    }
}

可以想象的是，如果没有Spy的话，我们是比较难以测试People这个类中行为的结果的。这就是一个最简单的Spy例子。

如果被调用了多次的时候，测试代码就类似如下：

@RunWith(MockitoJUnitRunner.class)
public class SeriousThingTest {
    @Mock
    private Logger spyLogger;


    @Captor
    private ArgumentCaptor<LogRecord> logRecordArgumentCaptor;


    @Test
    public void should_log_serious_thing() {
        new People(spyLogger).doSomethingSerious();

        verify(spyLogger, times(2)).log(logRecordArgumentCaptor.capture());

        final List<LogRecord> logRecords = logRecordArgumentCaptor.getAllValues();
        assertThat(logRecords.get(0).getLevel(), is(Level.WARNING));
        assertThat(logRecords.get(0).getMessage(), is("someone is doing something very dangerous"));

        assertThat(logRecords.get(1).getLevel(), is(Level.INFO));
        assertThat(logRecords.get(1).getMessage(), is("it is not so dangerous"));
    }
}


class People {
    private final Logger seriousLogger;

    public People(Logger seriousLogger) {
        this.seriousLogger = seriousLogger;
    }

    public void doSomethingSerious() {
        seriousLogger.log(new LogRecord(Level.WARNING, "someone is doing something very dangerous"));
        seriousLogger.log(new LogRecord(Level.INFO, "it is not so dangerous"));
    }
}