test: add integration test for subscriptions

package.json

@@ -189,6 +189,7 @@
     "fs-extra": "^11.2.0",
     "fs-teardown": "^0.3.0",
     "glob": "^11.0.0",
+    "graphql-ws": "^5.16.0",
     "jsdom": "^25.0.1",
     "json-bigint": "^1.0.0",
     "lint-staged": "^15.2.10",

test/node/graphql-api/graphql-subscription.test.ts

@@ -0,0 +1,62 @@
+// @vitest-environment node
+import { graphql } from 'msw'
+import { setupServer } from 'msw/node'
+import { createClient } from 'graphql-ws'
+
+const server = setupServer()
+
+beforeAll(() => {
+  server.listen()
+})
+
+afterEach(() => {
+  server.resetHandlers()
+})
+
+afterAll(() => {
+  server.close()
+})
+
+it('intercepts and mocks a GraphQL subscription', async () => {
+  const api = graphql.link('http://localhost:4000/graphql')
+
+  server.use(
+    api.pubsub.handler,
+    api.subscription('OnCommendAdded', () => {
+      api.pubsub.publish({
+        data: {
+          commentAdded: {
+            id: '1',
+            text: 'Hello world',
+          },
+        },
+      })
+    }),
+  )
+
+  const client = createClient({
+    url: 'ws://localhost:4000/graphql',
+  })
+
+  const subscription = client.iterate({
+    query: `
+subscription OnCommendAdded {
+  commentAdded {
+    id
+    text
+  }
+}
+    `,
+  })
+
+  await expect(subscription.next()).resolves.toMatchObject({
+    value: {
+      data: {
+        commentAdded: {
+          id: '1',
+          text: 'Hello world',
+        },
+      },
+    },
+  })
+})