Just found a (working) way to override current system time in a Java SE 8 JUnit test class powered by EasyMock, without PowerMock or Joda Time.
Here's what you need to do:
What needs to be done in the tested class
Step 1
Add a new java.time.Clock attribute to the tested class MyService and make sure the new attribute will instantiate properly at default values with an instantiation block or a constructor:
import java.time.Clock; import java.time.LocalDateTime; public class MyService { // (...) private Clock clock; public Clock getClock() { return clock; } public void setClock(Clock newClock) { clock = newClock; } public void initDefaultClock() { setClock( Clock.system( Clock.systemDefaultZone().getZone() // You can just as well use // java.util.TimeZone.getDefault().toZoneId() instead ) ); } { initDefaultClock(); // instantiation in an instantiation block, but // it can be done in a constructor just as well } // (...) } Step 2
Inject the new attribute clock into the method which calls for a current date-time. For instance, in my case I had to perform a check of whether a date stored in dataase happened before LocalDateTime.now(), which I remplaced with LocalDateTime.now(clock), like so:
import java.time.Clock; import java.time.LocalDateTime; public class MyService { // (...) protected void doExecute() { LocalDateTime dateToBeCompared = someLogic.whichReturns().aDate().fromDB(); while (dateToBeCompared.isBefore(LocalDateTime.now(clock))) { someOtherLogic(); } } // (...) } What needs to be done in the test class
Step 3
In the test class, create a mock clock object and inject it into the tested class's instance just before you call the tested method doExecute(), then reset it back right afterwards, like so:
import java.time.Clock; import java.time.LocalDateTime; import java.time.OffsetDateTime; import org.junit.Test; public class MyServiceTest { // (...) private int year = 2017; private int month = 2; private int day = 3; @Test public void doExecuteTest() throws Exception { // (...) EasyMock stuff like mock(..), expect(..), replay(..) and whatnot MyService myService = new MyService(); Clock mockClock = Clock.fixed( LocalDateTime.of(year, month, day, 0, 0).toInstant(OffsetDateTime.now().getOffset()), Clock.systemDefaultZone().getZone() // or java.util.TimeZone.getDefault().toZoneId() ); myService.setClock(mockClock); // set it before calling the tested method myService.doExecute(); // calling tested method myService.initDefaultClock(); // reset the clock to default right afterwards with our own previously created method // (...) remaining EasyMock stuff: verify(..) and assertEquals(..) } } Check it in debug mode and you will see the date of 2017 Feb 3 has been correctly injected into myService instance and used in the comparison instruction, and then has been properly reset to current date with initDefaultClock().