public void CalculateTax_ShouldReturn_Correct() { var grossSalary = 3400m; var expectedResult = 540m; var servicesCollection = new List <ITaxCalculator> { new SocialTaxService(), new IncomeTaxService() }; var salaryService = new SalaryService(servicesCollection); var result = salaryService.CalculateTaxes(grossSalary); Assert.AreEqual(expectedResult, result); }