@Test
public void removeInvalidContexts_4_InvalidContextsFound() {

    Set<Long> invalidContextsIds = notificationCourseAccessManager.removeInvalidContexts(subscriberIds);
    assertEquals(4, invalidContextsIds.size());
    assertTrue(invalidContextsIds.contains(contextId_privateCourse1));
    assertFalse(invalidContextsIds.contains(contextId_ok));
}