The need for cryogenic cold testing is dependent upon the requirements for the project. What codes and stadnards apply and what is the customer paying for.
Usually, and this is just a generalized statement, cold testing of production units is not done as it is expensive. Normally the design is qualified by testing and as long as it passes the normal ambient tests, the product is accepted. It is also common for some customers to ask for a smll percentage of a production lot to be tested at cryogenic temperatures.
For cryogenic valve testing, the most common standard is BS 6364. It is really for qualification of the design, but frequently the test method and leak rates from this standard are what customers ask for. Many large companies also have their own standard for cryogenic valve leak testing.