public void Delete_removes_one_item_from_db()
{
_sut.Delete(2);
Gutachter vorherKlaus = _inMemoryDbSet.FirstOrDefault(x => x.Id == 2);
Assert.That(vorherKlaus, Is.EqualTo(null), "The specified item must be deleted from DB");
_mockedContext.Verify(x => x.SaveChanges(), Times.Once());
}