public void GetForPaymentReturnsExpectNumbersOfPaymentInstrumentsForPayment()
        {
            IEnumerable <PaymentInstrument> instruments = _repository.GetByPaymentId(PAYMENT_ID);

            int totalCount = _expectedCounts.Select(eC => eC.Value).Sum();

            Assert.AreEqual(totalCount, instruments.Count());

            foreach (Type type in _expectedCounts.Keys)
            {
                if (_expectedCounts[type] != instruments.Count(instrument => instrument.GetType() == type))
                {
                    Assert.Fail("Count mismatch!");
                }
            }
        }