test: add runtime request handler test

test/browser/sse-api/sse.server.connect.test.ts

@@ -91,7 +91,7 @@ test('forwards message event from the server to the client automatically', async
     const { setupWorker, sse } = window.msw
 
     const worker = setupWorker(
-      sse(url, ({ client, server }) => {
+      sse(url, ({ server }) => {
         server.connect()
       }),
     )
@@ -102,8 +102,6 @@ test('forwards message event from the server to the client automatically', async
     return new Promise<void>((resolve, reject) => {
       const source = new EventSource(url)
       source.addEventListener('message', (event) => {
-        console.log('client got:', event.type, event.data)
-
         resolve(JSON.parse(event.data))
       })
       source.onerror = () => reject(new Error('EventSource connection failed'))

test/browser/sse-api/sse.use.test.ts

@@ -0,0 +1,58 @@
+import { setupWorker, sse } from 'msw/browser'
+import { test, expect } from '../playwright.extend'
+
+declare namespace window {
+  export const msw: {
+    setupWorker: typeof setupWorker
+    sse: typeof sse
+  }
+}
+
+test('supports server-sent event handler overrides', async ({
+  loadExample,
+  page,
+}) => {
+  await loadExample(require.resolve('./sse.mocks.ts'), {
+    skipActivation: true,
+  })
+
+  const workerRef = await page.evaluateHandle(async () => {
+    const { setupWorker, sse } = window.msw
+
+    const worker = setupWorker(
+      sse('http://localhost/stream', ({ client }) => {
+        client.send({ data: 'happy-path' })
+      }),
+    )
+    await worker.start()
+    return worker
+  })
+
+  await page.evaluate((worker) => {
+    const { sse } = window.msw
+
+    worker.use(
+      // Adding this runtime request handler will make it
+      // take precedence over the happy path handler above.
+      sse('http://localhost/stream', ({ client }) => {
+        // Queue the data for the next tick to rule out
+        // the happy path handler from executing.
+        queueMicrotask(() => {
+          client.send({ data: 'override' })
+        })
+      }),
+    )
+  }, workerRef)
+
+  const message = await page.evaluate(() => {
+    return new Promise((resolve, reject) => {
+      const source = new EventSource('http://localhost/stream')
+      source.addEventListener('message', (event) => {
+        resolve(event.data)
+      })
+      source.onerror = reject
+    })
+  })
+
+  expect(message).toBe('override')
+})