After a previous split with my H I made a similar mistake to Nick. My H had made it very clear he wanted sexual relations with me again and as a healthcare professional I felt very comfortable asking him to go for a STD check. I could tell by the look on his face that he had NEVER considered this an issue. I'd like to think that this was b/c he never had unprotected sex with the OW he had at that time. Thankfully I am not that naive. My H hates condoms with a vengenance! Anyway he went and had the test. I wanted us to go together. I knew I had nothing to hide b/c I haven't slept with anyone else since meeting H 20 years ago. He said he wanted to go alone b/c he knew I had nothing to hide and also to save me the embarrassment. Nearly 2 years on and 6 months after he left for the second time I found out that there had been more than one OW in the past. So obviously his true motivation for going alone was so that I did not find out this fact at the time. I NEVER considered that then.
So to sum up my ramble. What I am trying to say is yes, a test is imperative to protect your own health BUT a lot of hard work and trust rebuilding needs to happen before it should take place. If this means protected sex (or probably more sensible) no sex then so be it. IF the returning spouse truly wants to work on the whole M and not just on sexual relations they will understand and take things at a pace you can deal with. The same should go for the LBS.
Me 43 XH 45 M 2.7.88 Divorce 7.10.09 Kids D20,S17 & D15