It's great to see TAP support spreading to languages other than Perl. I've just switched to using it on a PHP project which is tested using TAP::Parser and it was a drop in replacement for my crufty implementation.
I have no real criticisms but some suggestions for future development:
* as noted in the source it'd be nice to have a recursive implementation of is_deeply that reported the location of the first difference
* implementing it on top of a layer equivalent to Perl's Test::Builder would make it easier for people to write additional assertion types.