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); }