@Test public void singletonTest() {
Assert.assertTrue(EnrolmentManager.getInstance() == EnrolmentManager.getInstance());
}
@Test public void createDeleteTest() {
Student s = new Student("Name");
ClassGroup cls = new ClassGroup("name", "description");
Enrolment enrol = EnrolmentManager.getInstance().addEnrolment(s, cls);
Assert.assertTrue(EnrolmentManager.getInstance().contains(enrol));
Assert.assertTrue(EnrolmentManager.getInstance().delete(enrol));
Assert.assertFalse(EnrolmentManager.getInstance().contains(enrol));