testland/websocket-tests
Use whenever the task is to test a WebSocket endpoint or real-time server: connect, send and receive messages, ping/pong, close codes, reconnect after the server drops, subprotocols and backpressure, with ws, Python websockets or Playwright.
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websocket-test-recipes.mdreferences/
WebSocket test recipes
Close-frame status codes and backpressure / large-message recipes. All codes and frame limits are per RFC 6455.
Close-frame status code matrix
Standard close codes:
| Code | Meaning |
|---|---|
| 1000 | Normal closure |
| 1001 | Endpoint going away |
| 1002 | Protocol error |
| 1006 | Abnormal closure (no close frame received) |
| 1011 | Server error |
Test the matrix per scenario:
test('server sends 1011 on internal error', async () => {
const ws = new WebSocket('ws://localhost:8080/');
await new Promise((r) => ws.once('open', r));
ws.send(JSON.stringify({ trigger: 'crash' }));
const code = await new Promise((r) => ws.once('close', (c) => r(c)));
expect(code).toBe(1011);
});
test('graceful shutdown sends 1001', async () => {
// server initiates shutdown; client observes 1001
const ws = new WebSocket('ws://localhost:8080/');
await new Promise((r) => ws.once('open', r));
await fetch('http://localhost:8080/admin/shutdown', { method: 'POST' });
const code = await new Promise((r) => ws.once('close', (c) => r(c)));
expect(code).toBe(1001);
});Verify: assert the observed close code equals the code the scenario should trigger; if it is 1006 (abnormal) instead, the server dropped the socket without a close frame - fix the server shutdown path before trusting the code matrix.
Backpressure / large message tests
Control frame payloads are <= 125 bytes; data frames have no upper
bound but implementations apply limits. Test the server's
maxPayload config:
test('server rejects message > maxPayload', async () => {
const ws = new WebSocket('ws://localhost:8080/');
await new Promise((r) => ws.once('open', r));
const big = 'a'.repeat(2 * 1024 * 1024); // 2 MB
ws.send(big);
const code = await new Promise((r) => ws.once('close', (c) => r(c)));
expect(code).toBe(1009); // Message too big
});