node.js: Cannot find module 'it-is'

i'm trying to run this node.js unit tests and i get this error:

module.js:340
    throw err;
      ^
Error: Cannot find module 'it-is'

from the code it's obvious that this 'it-is' module is a unit test module.. ie

var it = require('it-is');
...
it("Subject").equal(util.normalizeSubject("Re[2]:Subject"));

however it's pretty much impossible to google such a framework because google simply strips out the 'it-is' part.. and i search the node.js unit tests couldn't find something called 'it-is'..

help!