如何模拟 java.time.LocalDate.now()

In your code, replace LocalDate.now() with LocalDate.now(clock);.

You can then pass Clock.systemDefaultZone() for production and a fixed clock for testing.

This is an example :

First, inject the Clock. If you are using spring boot just do a :

@Bean
public Clock clock() {
return Clock.systemDefaultZone();
}

Second, call LocalDate.now(clock) in your code :

@Component
public class SomeClass{


@Autowired
private Clock clock;


public LocalDate someMethod(){
return LocalDate.now(clock);
}
}

Now, inside your unit test class :

// Some fixed date to make your tests
private final static LocalDate LOCAL_DATE = LocalDate.of(1989, 01, 13);


// mock your tested class
@InjectMocks
private SomeClass someClass;


//Mock your clock bean
@Mock
private Clock clock;


//field that will contain the fixed clock
private Clock fixedClock;




@Before
public void initMocks() {
MockitoAnnotations.initMocks(this);


//tell your tests to return the specified LOCAL_DATE when calling LocalDate.now(clock)
fixedClock = Clock.fixed(LOCAL_DATE.atStartOfDay(ZoneId.systemDefault()).toInstant(), ZoneId.systemDefault());
doReturn(fixedClock.instant()).when(clock).instant();
doReturn(fixedClock.getZone()).when(clock).getZone();
}


@Test
public void testSomeMethod(){
// call the method to test
LocalDate returnedLocalDate = someClass.someMethod();


//assert
assertEquals(LOCAL_DATE, returnedLocalDate);
}

You might also want to pass a fixed clock in production (the value of which is fixed at the start of a transaction) to avoid using inconsistent "now" in different entities and requests. See this question for details.

You can refactor you code to make it test-friendly, for example, replace all invocations of LocalDate.now() with invocation of some method of custom mockable non-static class.

Alternatively, you can use PowerMock's mockStatic.

If we need to mock static methods like now() we can use multiple alternatives like PowerMock:

@RunWith(PowerMockRunner.class)
@PrepareForTest({ LocalDateTime.class })
public class LocalDateTimeUnitTest {


@Test
public void givenLocalDateTimeMock_whenNow_thenGetFixedLocalDateTime() {
Clock clock = Clock.fixed(Instant.parse("2014-12-22T10:15:30.00Z"), ZoneId.of("UTC"));
LocalDateTime dateTime = LocalDateTime.now(clock);
mockStatic(LocalDateTime.class);
when(LocalDateTime.now()).thenReturn(dateTime);
String dateTimeExpected = "2014-12-22T10:15:30";


LocalDateTime now = LocalDateTime.now();


assertThat(now).isEqualTo(dateTimeExpected);
}
}

Or JMockit, indeed with JMockit we can use the MockUp class:

@Test
public void givenLocalDateTimeWithJMock_whenNow_thenGetFixedLocalDateTime() {
Clock clock = Clock.fixed(Instant.parse("2014-12-21T10:15:30.00Z"), ZoneId.of("UTC"));
new MockUp<LocalDateTime>() {
@Mock
public LocalDateTime now() {
return LocalDateTime.now(clock);
}
};
String dateTimeExpected = "2014-12-21T10:15:30";


LocalDateTime now = LocalDateTime.now();


assertThat(now).isEqualTo(dateTimeExpected);
}

Or the Expectations class:

@Test
public void givenLocalDateTimeWithExpectations_whenNow_thenGetFixedLocalDateTime() {
Clock clock = Clock.fixed(Instant.parse("2014-12-23T10:15:30.00Z"), ZoneId.of("UTC"));
LocalDateTime dateTimeExpected = LocalDateTime.now(clock);
new Expectations(LocalDateTime.class) {
{
LocalDateTime.now();
result = dateTimeExpected;
}
};


LocalDateTime now = LocalDateTime.now();


assertThat(now).isEqualTo(dateTimeExpected);
}

We can find more examples here.

Another simple alternative is to use the now() method with a fixed Clock instance. Certainly, most of the classes in java.time package have a now() method with a Clock parameter:

@Test
public void givenFixedClock_whenNow_thenGetFixedLocalDateTime() {
Clock clock = Clock.fixed(Instant.parse("2014-12-22T10:15:30.00Z"), ZoneId.of("UTC"));
String dateTimeExpected = "2014-12-22T10:15:30";


LocalDateTime dateTime = LocalDateTime.now(clock);


assertThat(dateTime).isEqualTo(dateTimeExpected);
}

Using Spring:

ClockConfiguration class:

@Configuration
public class ClockConfiguration {
private final static LocalDate LOCAL_DATE = LocalDate.of(2019, 12, 17);


@Bean
@ConditionalOnMissingBean
Clock getSystemDefaultZoneClock() {
return Clock.systemDefaultZone();
}


@Bean
@Profile("test")
@Primary
Clock getFixedClock() {
return Clock.fixed(LOCAL_DATE.atStartOfDay(ZoneId.systemDefault()).toInstant(), ZoneId.systemDefault());
}
}

SomeService class:

@Service
@RequiredArgsConstructor
public class SomeService {


private final Clock clock;


public void someMethod(){
...


LocalDateTime.now(clock)
LocalDate.now(clock)


...
}
}

You must have an active "test" profile in the test:

SomeServiceTest class:

@ActiveProfiles("test")
@EnableConfigurationProperties
@SpringBootTest(classes = [YourAppMainClass])
class SomeServiceTest {
...
}

You can use supplier inside your class which you are testing to pass current time wherever date time is used.

public Supplier<LocalDateTime> localDateTime = () -> LocalDateTime.now();

and in the test method just override its value like :

myClassObj.localDateTime = () -> LocalDateTime.parse("2020-11-24T23:59:59.999");

We have to mock a static method here. I use following dependency. Remember all our test code has to be in the try block. As soon as we call LocalDate.now() or LocalDate

<!-- https://mvnrepository.com/artifact/org.mockito/mockito-inline -->
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-inline</artifactId>
<version>3.11.0</version>
<scope>test</scope>
</dependency>

The code:

 @Test
void verifykNonLeapYear() {


LocalDate currentLocalDate = LocalDate.of(2010, 2, 13);
try (MockedStatic<LocalDate> topDateTimeUtilMock = Mockito.mockStatic(LocalDate.class)) {
topDateTimeUtilMock.when(() -> LocalDate.now()).thenReturn(currentLocalDate);
assertThat(TopDateTimeUtil.numberOfDaysInCurrentYear(), is(365));
}
}