All of the unit testing frameworks that I know of / can find require a test runner.
They all require you to globally install and run some program that runs your tests. Is there a well supported testing framework that can run as an npm require() ?
I need one like this because I want to be able to debug my tests, and it is much easier for me to do this though webstorm. Also, the project I'm working on is very small and I don't want to get fancy
The node.js project itself simply uses the built-in assert module and JavaScript exceptions. They have a fairly straightforward script that runs every .js file in a directory tree and if the file doesn't throw any exceptions, the test is considered passing. You could use something like that.
However, although most frameworks do have a command line runner, you absolutely never need to install them (or anything) with -g. If you understand the basic concept of the unix PATH environment variable, you can npm install --save-dev mocha (for example) and then run your tests with ./node_modules/.bin/mocha. No -g required.
See also http://peterlyons.com/problog/2012/09/managing-per-project-interpreters-and-the-path