public void CantDeleteNotExistingContractor()
        {
            using (EF_ZMT_DbContext.EF_ZMT_DbContext context = new EF_ZMT_DbContext.EF_ZMT_DbContext())
            {
                FixedAssetService transaction = new FixedAssetService();
                context.Context.ExecuteStoreCommand("DELETE FROM Contractor");
                int count = context.Context.Contractors.Count();
                Assert.AreEqual(count, 0);

                Contractor contractor = new Contractor()
                {
                    name = "ABC",
                    city = "Kraków",
                    nip = 555123213,
                    postal_code = "31-987",
                    street = "Królewska",
                    country = "Polska"
                };
                transaction.DeleteContractor(contractor);
                count = context.Context.Contractors.Count();
                Assert.AreEqual(count, 0);
   
            }
        }
        public void CanDeleteContractor()
        {
            using (EF_ZMT_DbContext.EF_ZMT_DbContext context = new EF_ZMT_DbContext.EF_ZMT_DbContext())
            {
                FixedAssetService transaction = new FixedAssetService();
                context.Context.ExecuteStoreCommand("DELETE FROM Contractor");
                int count = context.Context.Contractors.Count();
                Assert.AreEqual(count, 0);

                Contractor contractor = new Contractor()
                {
                    name = "ABC",
                    city = "Kraków",
                    nip = 555123213,
                    postal_code = "31-987",
                    street = "Królewska",
                    country = "Polska"
                };
                transaction.AddContractor(contractor);
                count = context.Context.Contractors.Count();
                Assert.AreEqual(count, 1);

                Contractor temp = context.Context.Contractors.FirstOrDefault(x => x.name == "ABC");
                transaction.DeleteContractor(temp);
                count = context.Context.Contractors.Count();
                Assert.AreEqual(count, 0);

                temp = context.Context.Contractors.FirstOrDefault(x => x.name == "ABC");
                Assert.IsNull(temp);
            }
        }