fix: jest bug when using MockScope.delay

lib/api/api-request.js

@@ -88,14 +88,16 @@ class RequestHandler extends AsyncResource {
     this.res = body
     const headers = this.responseHeaders === 'raw' ? util.parseRawHeaders(rawHeaders) : util.parseHeaders(rawHeaders)
 
-    this.runInAsyncScope(callback, null, null, {
-      statusCode,
-      headers,
-      trailers: this.trailers,
-      opaque,
-      body,
-      context
-    })
+    if (callback !== null) {
+      this.runInAsyncScope(callback, null, null, {
+        statusCode,
+        headers,
+        trailers: this.trailers,
+        opaque,
+        body,
+        context
+      })
+    }
   }
 
   onData (chunk) {

test/jest/mock-scope.test.js

@@ -0,0 +1,32 @@
+const { MockAgent, setGlobalDispatcher, request } = require('../../index')
+
+/* global afterAll, expect, it, AbortController */
+
+const runIf = (condition) => condition ? it : it.skip
+
+const nodeMajor = Number(process.versions.node.split('.', 1)[0])
+const mockAgent = new MockAgent()
+
+afterAll(async () => {
+  await mockAgent.close()
+})
+
+runIf(nodeMajor >= 16)('Jest works with MockScope.delay - issue #1327', async () => {
+  mockAgent.disableNetConnect()
+  setGlobalDispatcher(mockAgent)
+
+  const mockPool = mockAgent.get('http://localhost:3333')
+
+  mockPool.intercept({
+    path: '/jest-bugs',
+    method: 'GET'
+  }).reply(200, 'Hello').delay(100)
+
+  const ac = new AbortController()
+  setTimeout(() => ac.abort(), 5)
+  const promise = request('http://localhost:3333/jest-bugs', {
+    signal: ac.signal
+  })
+
+  await expect(promise).rejects.toThrowError('Request aborted')
+}, 1000)