How to use Mockito stubs in a JUnitParams parameter provider?

I am trying to learn JUnit. Working on a particular problem I decided to use JUnitParams parameter providers. Each set of parameters for a test method I'm writing should contain two input values and a list against which results of a method call would be tested:

private static final Object[] getConstraints() { return new Object[]{ new Object[]{15, Equipment.WHITEBOARD, Arrays.asList(new Classroom[]{classroomA, classroomB})}, new Object[]{15, Equipment.PROJECTOR, Arrays.asList(new Classroom[]{classroomB})}, new Object[]{15, Equipment.MICROPHONE, Arrays.asList(new Classroom[]{classroomA})}, new Object[]{30, Equipment.WHITEBOARD, Arrays.asList(new Classroom[]{classroomB})}, new Object[]{30, Equipment.PROJECTOR, Arrays.asList(new Classroom[]{classroomB})}, new Object[]{30, Equipment.MICROPHONE, Arrays.asList(new Classroom[]{})}, new Object[]{45, Equipment.WHITEBOARD, Arrays.asList(new Classroom[]{})}, new Object[]{45, Equipment.PROJECTOR, Arrays.asList(new Classroom[]{})}, new Object[]{45, Equipment.MICROPHONE, Arrays.asList(new Classroom[]{})}, }; } 

classroomA and classroomB are actually Mockito stubs prepared before each test execution:

@Before public void setUp() { classroomA = mock(Classroom.class); classroomB = mock(Classroom.class); classrooms = Arrays.asList(new Classroom[]{classroomA, classroomB}); when(classroomA.getName()).thenReturn("A"); when(classroomA.getCapacity()).thenReturn(20); when(classroomA.getEquipment()).thenReturn(Arrays.asList(new Equipment[]{Equipment.WHITEBOARD, Equipment.MICROPHONE})); when(classroomB.getName()).thenReturn("B"); when(classroomB.getCapacity()).thenReturn(40); when(classroomB.getEquipment()).thenReturn(Arrays.asList(new Equipment[]{Equipment.WHITEBOARD, Equipment.PROJECTOR})); bookingSystem = new BookingSystem(classrooms); } 

The problem occurs when I try to use aforementioned lists of Classroom objects:

@Test @Parameters(method = "getConstraints") public void shouldBookClassroomMeetingConstraints(int capacity, Equipment equipment, List<Classroom> suitableClassrooms) { Assert.assertTrue("Should book a classroom that has a minimum capacity of " + capacity + " and has " + equipment, suitableClassrooms.contains(bookingSystem.book(capacity, equipment, ANY_DAY_OF_WEEK, ANY_HOUR))); } 

Debugging shows that during the first run suitableClassrooms contains 2 objects, but further inspection shows that all elements are null - the stubs I prepared are not there. Obviously, the tests don't pass or fail where they should pass or fail.

Is there a limitation on using JUnitParams with Mockito or am I using them wrong? What is the right way to use them?

It is also possible that this is a wrong technique of unit testing. If this is the case, what is the proper way of writing a test that verifies if the result of a method call is in a given array?