public void GetUnpaidBillByPatientId_NoneExistsPatientId_ReturnsNull()
{
int patientId = -1;
bill actual = _sut.GetUnpaidBillByPatientId(patientId);
actual.Should().BeNull();
}
public void PayBill_ValidBillId_ChangesBillStatus()
{
int id = 1;
var billUpdated = new bill();
_sut.PayBill(id);
billUpdated.Should().BeOfType <bill>().Which.is_paid.Should().BeTrue();
}