How can I mock java.time.LocalDate.now()
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);
}
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);
}