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?