java - LocalDateTime.of returns null -

i trying unit test code uses java.time.localdatetime. i'm able mock working, when add time (either minutes or days) end null value.

@runwith(powermockrunner.class) @preparefortest({ localdatetime.class }) public class localdatetimemocktest {     @test     public void shouldcorrectlycalculatetimeout()     {         // arrange         powermockito.mockstatic(localdatetime.class);         localdatetime fixedpointintime = localdatetime.of(2017, 9, 11, 21, 28, 47);         bddmockito.given(localdatetime.now()).willreturn(fixedpointintime);          // act         localdatetime fixedtomorrow = localdatetime.now().plusdays(1); //shouldn't have npe?          // assert         assert.asserttrue(localdatetime.now() == fixedpointintime); //edit - both null         assert.assertnotnull(fixedtomorrow); //test fails here         assert.assertequals(12, fixedtomorrow.getdayofmonth());     } } 

i understand (well think do) localdatetime immutable, , think should new instance instead of null value.

turns out .of method giving me null value. why?

according documentation:

use powermock.mockstatic(classthatcontainsstaticmethod.class) mock all methods of class.

and:

note can mock static methods in class though class final. method can final. to mock specific static methods of class refer partial mocking section in documentation.

to mock static method in system class need follow this approach.

you told mock static methods, didn't supply mock of() method.

solution: either add mock of() method, or change use partial mocking, of() method not mocked.

basically, read , follow instructions of documentation.