testem: Auto-Launch not working when run from npm

I just updated to Node 5.0.0 with NPM 3.3.6. I’m running on OSX 10.10.5 (Yosemite)

I have a “test” script defined in my project.json:

"scripts": {
    "test": "testem",
    "test-ci": "testem ci --port 17357"
  }

So when I run npm test, it starts testem.

The problem is that my launch_in_dev browser (Chrome) is not auto-run. Even if I call it out explicitly: "test": "testem -l Chrome", the browser does not auto-launch. Testem DOES start, but the browser does not. I can run it by hand, and that works. It’s just odd.

Running the tests by hand: ./node_modules/.bin/testem DOES work… it just seems like this use case is being blocked. And, this used to work (node 0.12 + NPM 2).

Does anyone know a workaround? I try to avoid installing testem globally and prefer to do everything via npm run commands.