Support WebSocket endpoints

[josselinonduty]

h3/nitro provides websocket support (experimental in v2, supported in v3 nitrojs/nitro#3766).
Are there any plans to include ws testing in nitro-test-utils?

[johannschopplich]

Hi there, I investigated this and the implementation itself is straightforward (connect, send, receive queue with timeout, close), but the Nitro v3 dev server architecture currently prevents it from working:

The dev server runs your app in a worker thread (via env-runner). HTTP requests get proxied to the worker via httpxy.proxyFetch. WebSocket upgrades use httpxy.proxyUpgrade, which forwards the raw TCP upgrade to the worker's internal srvx server. However, the Nitro dev entry exports an upgrade handler (for crossws) but not a websocket property... so the worker's srvx server processes the proxied upgrade as a regular HTTP request (returning 426) before the raw Node "upgrade" event can fire to complete the handshake. The connection appears to open from the client's perspective, but no messages are relayed.

This would need a fix upstream in Nitro (likely the dev entry should export websocket hooks so the worker's srvx crossws plugin handles upgrades directly, rather than relying on the raw node server event racing with srvx's HTTP handler).

I'll keep the issue open and revisit once Nitro's dev server WebSocket proxying is resolved.