A common test is ASTM F519-05, 'Standard Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating Processes and Service Environments.'
http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/F519.htm?E+mystore

It uses pre-machined specimens of hardened 4340 steel which are processed (e.g., chrome plated) along with your production parts. GREEN SPECIALTY SERVICE INC sells the various type geometries; I think that most common is the tension test specimen with threaded ends. http://www.greenspecialty.com/
They also show some aircraft panels (which don't look like steel to me) which may be for some other hydrogen embrittlement test of possible interest to you.

Another test, which can compare hydrogen embrittlement susceptibilities of different steels, is
ASTM F1624-06 Standard Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique
http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/F1624.htm?E+mystore