public void TestActivateMembershipsPreventDuplicates()
{
var customer = new Customer {
Id = 1
};
Assert.IsEmpty(customer.Memberships);
var customerService = new CustomerService();
customerService.ActivateMembership(customer, MembershipType.Other);
customerService.ActivateMembership(customer, MembershipType.Other);
customerService.ActivateMembership(customer, MembershipType.BookClubMembership);
Assert.IsTrue(customer.Memberships.Count == 2);
Assert.IsTrue(customer.Memberships.Contains(MembershipType.Other));
Assert.IsTrue(customer.Memberships.Contains(MembershipType.BookClubMembership));
}
