New building pressure test - camera inspection drainage meaningful?

Hello dear professionals!

We are currently building a house with a prefab house company. So far, the foundation slab has been completed and the drainage pipes have been laid below and outside the foundation slab and connected to the sewer. Below the foundation slab by the prefab house company and outside by our earthworks contractor. Is it advisable to have a plumbing company perform a pressure test or a camera inspection of the drainage pipes to detect leaks? And should we better do that immediately now or only once the house is built and the supply lines have been installed, in case there is damage to the drainage? A pressure test is not mandatory for us.

A pressure test is not mandatory for us.

The only thing I would have checked, as long as it is not already mandatory, would be the backflow flap, if present.

The only thing I would have checked, as long as it is not already mandatory, would be the backwater valve, if present.

Thank you for the answer. A backwater valve is not required. What is the general experience with defects in drainage pipes? Does it often happen in new construction that the pipes are leaking or damaged? How would we notice a leak in the drainage pipes below the floor slab if we do not perform a pressure test? Would we even notice it, or would it actually be irrelevant due to the horizontal sealing above the pipes?

If anyone else has experience with the topic, I would be very grateful for feedback.