I had a really friendly email this week, after contacting me when I was on a day off last weekend with "R u available" (I do have an availability tab with this info on it) one line, no greeting message a few days later he sent "Do u get tested regular?".

I replied "Of course not"

Then I sent him another reply explaining why he shouldn't take anyone's word for it, an SP is hardly going to say "Oh, no I don't bother about my sexual health", whether she does or not it's only she knows the truth.

It is an annoying question, the one "are you clean" - I often bounce back with "No-one can guarantee anything, to do so would be ethically wrong. Do you get tested?".

I had a reg saying he thought he had caught chlamydia and asked me when the last time I got tested (for me its every 8-12 weeks)
He got himself all worked up, saying his marriage would be over etc if he had caught it- i told him it was unlikely I had anything, as touch wood, I haven't caught anything before, and I only offer owo, so it is less risk that BB.
Anyway both got the results back (I took the test earlier than normal because he worried me) both came back clear, thank god.
But i do think these guys if they have to much to lose, then they shouldn't be doing anything unprotected with a wg 

I don't mind clients asking if I get tested.

But I think some clients are a little deluded that if they are in a relationship that they don't think their partners would cheat on them and possibly pass on an sti.  As if they can cheat why can't their partner!