From [npm help folders](https://npmjs.org/doc/files/npm-folders.html#Executables):

> When in local mode, executables are linked into ./node_modules/.bin so that they can be made available to scripts run through npm. (For example, so that a test runner will be in the path when you run npm test.)

Which means after installing traceur like this:

1. git clone ...
2. cd traceur-compiler
3. npm install

for me `mocha` is available as `node_modules/.bin/mocha`. Running `npm test` after those steps fails because I don't have it installed globally.

It's perhaps also better if the tests are using the local mocha version instead of whatever is in $PATH?