@Test public void testItScrollsToPreviousMonth() { // Sun, 08 Feb 2015 00:00:00 GMT underTest.setCurrentDate(new Date(1423353600000L)); underTest.showPreviousMonth(); Date actualDate = underTest.getFirstDayOfCurrentMonth(); // Thu, 01 Jan 2015 00:00:00 GMT - expected assertEquals(new Date(1420070400000L), actualDate); }