public void TestFirst()
{
var employees = RepositoryFactory.GetEmployees();
Assert.Equal("Kevin", WithoutLinq.CashFirst(employees, a => a.MonthSalary > 200).Name);
Assert.Throws <ArgumentNullException>(() => WithoutLinq.CashFirst(employees, a => a.MonthSalary > 500));
Assert.Equal("Kevin", employees.CashFirst(a => a.MonthSalary > 200).Name);
Assert.Throws <ArgumentNullException>(() => employees.CashFirst(a => a.MonthSalary > 500));
}