I might be missing something because I'm not familiar with hypothesis and how you're using it to generate test cases, but it looks like malformed JP/RJP aren't being covered. I looked at the creation tests and those all seem to test valid forms.

I messed up the regex changes for index adjustment (#47) in an astonishing number of ways before sorting it out, so I wanted to cover those problems. I wrote up some test cases for both regular and relative JSON Pointers in a gist.

These could be handled in a similar way as the evaluation tests. They could even be folded into that by adding a <malformed> outcome and wrapping the construction in a try, but that gets a bit awkward as the starting point and the document to evaluate against are irrelevant. So it's probably better to have a separate data file and test function.

If this seems reasonable, I will submit a PR for it.