The either type encodes values with two possibilities. Namely, the Right and Left constructor represent the first and second possibility, respectively.
Fantasy Eithers uses nodeunit for all the tests and because of this there is currently an existing adapter in the library to help with integration between nodeunit and Fantasy Check.
Currently Fantasy Check is using Istanbul for code coverage analysis; you can run the coverage via the following command:
This assumes that you have istanbul installed correctly.
istanbul cover nodeunit -- test/*.js