Install dependencies:

npm install

Run tests (CI mode):

npm test

Interactive dev:

node ../../testem.js

Testem serves the browser and the Testem client (/testem.js, Socket.IO). This example embeds Vite middleware mode ahead of Testem’s static file handler so @vite/client–style module resolution works for your entry HTML.

The vite-plugin-testem package (installed as a dev dependency) provides:

1. vitePluginTestem() — a Vite plugin that can inject /testem.js (and the TAP bridge for framework: 'tap'). This example loads /testem.js explicitly in index.html in the same order as Testem’s Mocha runner template, so the plugin does not add a second copy.
2. createTestemViteMiddleware() — builds a Vite dev server in middleware mode and returns Express middleware for Testem’s middleware config. It skips URLs that belong to Testem so the client still loads from the same origin.

See the package README for full API details and the recommended on_exit handler when using the middleware.

HMR is turned off in middleware mode here because Testem’s Express app would need explicit wiring to Vite’s WebSocket server; you can still get fast feedback from Testem’s file watching and reloads.

testem.js uses on_exit to call the Vite server’s close() hook so watchers and other resources shut down cleanly when Testem exits.

index.html loads Mocha’s prebuilt browser bundle mocha/mocha.js (the UMD file shipped in the package) with plain <script> tags, then /testem.js, then mocha.setup('bdd'), matching the usual Testem order. The test file is a module so you can import Chai and your sources; it finishes with mocha.run().

Importing the package entry (import mocha from 'mocha') pulls in code paths that expect Node’s process while Vite prebundles; using the prebuilt mocha.js avoids that.

For comparison with other ecosystems: karma-vite embeds Vite in Karma; this setup does the analogous thing for Testem’s Express stack. Embroider’s Vite integration targets Ember apps; web-test-runner’s Vite plugin targets Web Test Runner.