.testem.json

{
    "launchers": {
        "node": {
            "command": "npm test"
        }
    },
    "src_files": [
        "./**/*.js"
    ],
    "before_tests": "npm run build",
    "on_exit": "rm test/static/bundle.js",
    "test_page": "test/static/index.html",
    "launch_in_dev": ["node", "phantomjs"]
}