I don't greatly like the way that the regression test case filters the output; it hides too much IMO. I'd be inclined to try to return the EXPLAIN output with as much detail preserved as possible. Maybe we could use regex substitution on lines of the output to get rid of stuff that won't be invariant.
My first thought was to do a regex over the explain output to mask the troublesome value, but I couldn't figure out how to make it work and didn't find an example (admittedly didn't spent a huge amount of time hunting though). I'd love to see how to put it together.