Introduction

Mock Config supports Server-Sent Events through the rest.sse and rest.stream helpers provided by the library:

import { rest } from 'mock-config-server';

rest.sse('/notifications', ({ client }) => {
  client.send('Connected', { event: 'status' });
  client.send('New message', { event: 'message', id: '1' });
  client.close();
});

SSE is built on top of HTTP, but long-lived event streams are easier to describe with a dedicated helper. Mock Config sets the event-stream response headers for you and gives the handler a client for pushing messages over time.

Use rest.sse for GET streams opened with EventSource. Use rest.stream for POST streams when the client sends a request body before reading the response.

Benefits

Here are some of the benefits of using Mock Config for SSE mocking:

• stream-first: push multiple events from one handler
• ergonomic: use client.send(), client.close(), and setDelay()
• request-aware: read params, queries, headers, cookies, and request body in handlers
• scenario-driven: combine streams with Matcher and Interceptors
• coexists with REST and GraphQL: SSE mocks run in the same server instance