The E&M diagnostic I have is that by Hieggelke and O'Kuma. Actually, it's a set of three instruments: Conceptual Survey in Electricity and Magnetism, Conceptual Survey in Electricity, and Conceptual Survey in Magnetism.
A few of you have asked me for copies. I'm not comfortable about distributing these instruments without the authors' permissions. I have Hieggelke's email as curth@jjc.cc.il.us and O'Kuma's email as tlo@lee.edu. I hope they don't mind my giving their email addresses.