Merge branch 'winh-rejected-jest-promises' into 'master'

Fail Jest tests for unhandled Promise rejections

Closes #56053

See merge request gitlab-org/gitlab-ce!26424

spec/frontend/environment.js

@@ -27,6 +27,25 @@ class CustomEnvironment extends JSDOMEnvironment {
     this.global.gon = {
       ee: testEnvironmentOptions.IS_EE,
     };
+
+    this.rejectedPromises = [];
+
+    this.global.promiseRejectionHandler = error => {
+      this.rejectedPromises.push(error);
+    };
+  }
+
+  async teardown() {
+    await new Promise(setImmediate);
+
+    if (this.rejectedPromises.length > 0) {
+      throw new ErrorWithStack(
+        `Unhandled Promise rejections: ${this.rejectedPromises.join(', ')}`,
+        this.teardown,
+      );
+    }
+
+    await super.teardown();
   }
 }
 

spec/frontend/test_setup.js

@@ -5,10 +5,15 @@ import axios from '~/lib/utils/axios_utils';
 import { initializeTestTimeout } from './helpers/timeout';
 import { getJSONFixture, loadHTMLFixture, setHTMLFixture } from './helpers/fixtures';
 
-// wait for pending setTimeout()s
-afterEach(() => {
+process.on('unhandledRejection', global.promiseRejectionHandler);
+
+afterEach(() =>
+  // give Promises a bit more time so they fail the right test
+  new Promise(setImmediate).then(() => {
+    // wait for pending setTimeout()s
     jest.runAllTimers();
-});
+  }),
+);
 
 initializeTestTimeout(300);