Coverage tests

Tools are tested against test262, babel and TypeScript for conformance.

Clone the test repositories beforehand:

just submodules

Development

# full run
cargo coverage
cargo coverage js # for test262
cargo coverage babel # for babel
cargo coverage ts # for typescript

# run in watch
cargo watch -x 'coverage js'

# filter for a file path
cargo watch -x 'coverage js --filter filter-file-path'

# find crash scene by turning off rayon and print out the test cases in serial
cargo coverage -- --debug

# Run after submodules are updated
UPDATE_SNAPSHOT=1 just c