public void SubscriptionsService_AddPurchase_calls_Create_method()
{
int userId = 74;
bool isCreateCalled = false;
var mock = new Mock <IUnitOfWork>();
mock.Setup(a => a.Purchases.Create(It.Is <Purchase>(p =>
(p.UserId == userId) &&
(p.IsPaid == false)))).Callback(() => isCreateCalled = true);
service = new SubscriptionsService(mock.Object);
service.AddPurchase(userId);
Assert.IsTrue(isCreateCalled);
}