Size is required before adding to bag

Interview scenario

"On the product page, Add to Bag without a size should show an error. Cover that, then pick an in-stock size, add to bag, and check the bag shows the right item and size. Also assert that the out-of-stock size can't be selected."

Acceptance criteria

1. Open the Roadway Men Slim Fit Casual Shirt (search shirt, click the card).
2. Click ADD TO BAG without a size and assert "Please select a size".
3. Assert size XL is disabled (out of stock).
4. Select size M, add to bag, assert the bag count is 1, open the bag and assert size M.