public void CountContractors()
        {
            Mock<IContractorRepository> mock = new Mock<IContractorRepository>();
            mock.Setup(a => a.Contractors).Returns(new Contractor[]
            {
                new Contractor { id = 1, name = "Firma1" },
                new Contractor { id = 2, name = "Firma2" },
                new Contractor { id = 3, name = "Firma3" },
                new Contractor { id = 4, name = "Firma4" },
                new Contractor { id = 5, name = "Firma5" },
                new Contractor { id = 6, name = "Firma6" }
            }.AsQueryable());

            ContractorController ctrl = new ContractorController(mock.Object);
            Assert.AreEqual(ctrl.CountContractors(), 6);
        }