@Test
public void testToString() {

    User user = new User(1, "jad", "jane21@gmail.com", "Jane", "Doe");
    assertEquals("User [userId=1, username=jad, email=jane21@gmail.com, firstname=Jane, lastname=Doe]", user.toString());
    User userWithNullStrings = new User(1, null, null, null, null);
    assertEquals("User [userId=1, username=null, email=null, firstname=null, lastname=null]", userWithNullStrings.toString());
}