test: add fuzzing set up

[DavidKorczynski]

This is an effort to migrate fuzzers from OSS-Fuzz to upstream.

I've added it such that it's also a unit test that is run by way of pytest. The reason for doing so is to make it easier to test that the fuzzers won't break during development.

If you are interested in this addition, then I can refine the build script on the OSS-Fuzz side (https://github.com/google/oss-fuzz/blob/master/projects/coveragepy/build.sh) such that it builds all files prefixed test_fuzz in the tests/ directory as fuzzers and will run them on OSS-Fuzz accodingly. This will make it trivial to add new fuzzers to the continuous fuzzing set up.

Ref:

• https://github.com/google/oss-fuzz/pull/8161
• https://github.com/nedbat/coveragepy/pull/1490

Signed-off-by: David Korczynski [email protected]

[ProsperousHeart]

Are this and #1490 still valid?