One way valves, check valves, or non-return valves - whatever terminology you use, they are quite a common features of medical devices. They are usually inexpensive but if they fail to operate as designed the consequences can be disastrous.
Uson has a new blog post describing the leak testing of one way valves using a Sprint iQ leak tester and a downstream pressure sensor. The company has a downloadable application note for members of the Uson Literature Club. To read the blog post go to http://www.uson.com/leak-testing-blog/leak-testing-one-way-valves/ where you will find instructions on how to join the literature club and download the application note.