public void VendingMachineItem_should_decrement_the_Quantity() { var testOrderNumber = _fixture.Create <int>(); var testProductName = _fixture.Create <string>(); var testPrice = _fixture.Create <decimal>(); var testTotalItem = _fixture.Create <int>(); var testPurchaseQuantity = 1; var cut = new MM(testOrderNumber, testProductName, testPrice, testTotalItem); cut.DecrementItem(testPurchaseQuantity); cut.TotalItem.Should().Be(testTotalItem - testPurchaseQuantity); }