Creating Order for LoggedIn existing customer and verifying decreasing of product quantity in Stock after placing order

PreConditions
Customer with default Shipping and Billing address is created
"Simple product 1" created with quantity 100 on default Source

1. Goto frontend Home Page
2. Login into your customer account
3. Add to cart "Simple product 1" quantity 5 items
4. Open your shopping cart
5. Click on "Proceed to Checkout" button - You are redirected to "Checkout" page - Shipping information
6. Select your shipping address
7. Specify shipping method - Fixed - Flat rate
8. Click "Next" - You are redirected to "Payment" step
9. Specify Payment method - Check/Money Order
10. Select your billing address
11. Click "Place Order"
12. You are redirected to "Success" page.
13. Verify succcess message "Thank you for your purchase! Your order number is: ########. We'll email you an order confirmation with details and tracking info."
14. Click on your order number to verify order information in Your customer account page
15. Login to admin
16. Goto te to Catalog > Products
17. Open "Simple Product 1" product page in Admin
18. Verify that Stock Quantity of "Simple Product 1" is decreased to 95
19. Verify in Sources field that Qty of "Simple Product 1" is decreased to 95