I wrote Blackjack in Elisp. It allows you to play Blackjack in your Emacs editor.
You can install it from MELPA:
M-x package-install blackjack
make test and
make test-coverage are available. Tests are written using Buttercup. Test coverage is generated using undercover. Both packages are available from MELPA.
You will need to install Ruby and Simplecov for test coverage to build.