Fail for unhandled Promise rejections in Jest

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

@@ -3,6 +3,8 @@ import Translate from '~/vue_shared/translate';
 import axios from '~/lib/utils/axios_utils';
 import { initializeTestTimeout } from './helpers/timeout';
 
+process.on('unhandledRejection', global.promiseRejectionHandler);
+
 // wait for pending setTimeout()s
 afterEach(() => {
   jest.runAllTimers();