如何使用Mockito在java中模拟新的Date()

Question

我有一个使用当前时间进行一些计算的函数.我想用mockito嘲笑它.

我要测试的类的一个例子:

public class ClassToTest {
    public long getDoubleTime(){
        return new Date().getTime()*2;
    }
}

我喜欢这样的东西:

@Test
public void testDoubleTime(){
   mockDateSomeHow(Date.class).when(getTime()).return(30);
   assertEquals(60,new ClassToTest().getDoubleTime());
}

有可能嘲笑吗？我不想更改"经过测试"的代码以便进行测试.

Answer 1

正确的做法是重新构建代码,使其更易于测试,如下所示.重构代码以删除对Date的直接依赖将允许您为正常运行时和测试运行时注入不同的实现:

interface DateTime {
    Date getDate();
}

class DateTimeImpl implements DateTime {
    @Override
    public Date getDate() {
       return new Date();
    }
}

class MyClass {

    private final DateTime dateTime;
    // inject your Mock DateTime when testing other wise inject DateTimeImpl

    public MyClass(final DateTime dateTime) {
        this.dateTime = dateTime;
    }

    public long getDoubleTime(){
        return dateTime.getDate().getTime()*2;
    }
}

public class MyClassTest {
    private MyClass myClassTest;

    @Before
    public void setUp() {
        final Date date = Mockito.mock(Date.class);
        Mockito.when(date.getTime()).thenReturn(30L);

        final DateTime dt = Mockito.mock(DateTime.class);
        Mockito.when(dt.getDate()).thenReturn(date);

        myClassTest = new MyClass(dt);
    }

    @Test
    public void someTest() {
        final long doubleTime = myClassTest.getDoubleTime();
        assertEquals(60, doubleTime);
    }
}

Answer 2

如果你有遗留的代码,你不能重构,你不想影响System.currentTimeMillis(),请尝试使用Powermock和PowerMockito

//note the static import
import static org.powermock.api.mockito.PowerMockito.whenNew;

@PrepareForTest({ LegacyClassA.class, LegacyClassB.class })

@Before
public void setUp() throws Exception {

    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    sdf.setTimeZone(TimeZone.getTimeZone("PST"));

    Date NOW = sdf.parse("2015-05-23 00:00:00");

    // everytime we call new Date() inside a method of any class
    // declared in @PrepareForTest we will get the NOW instance 
    whenNew(Date.class).withNoArguments().thenReturn(NOW);

}

public class LegacyClassA {
  public Date getSomeDate() {
     return new Date(); //returns NOW
  }
}

Answer 3

你可以通过使用PowerMock 来实现这一点,它可以增强Mockito能够模拟静态方法.然后你可以模拟System.currentTimeMillis(),这是new Date()最终得到时间的地方.

你可以.我不会就你是否应该提出意见.