Migrate old notes app test from Karma to Jest

app/assets/javascripts/notes.js

@@ -7,6 +7,10 @@ no-unused-vars, no-shadow, no-useless-escape, class-methods-use-this */
 /* global ResolveService */
 /* global mrRefreshWidgetUrl */
 
+/*
+old_notes_spec.js is the spec for the legacy, jQuery notes application. It has nothing to do with the new, fancy Vue notes app.
+ */
+
 import $ from 'jquery';
 import _ from 'underscore';
 import Cookies from 'js-cookie';

spec/frontend/helpers/jest_helpers.js

+/* eslint-disable import/prefer-default-export */
+
+/*
+@module
+
+This method provides convenience functions to help migrating from Karma/Jasmine to Jest.
+
+Try not to use these in new tests - this module is provided primarily for convenience of migrating tests.
+ */
+
+/**
+ * Creates a plain JS object pre-populated with Jest spy functions. Useful for making simple mocks classes.
+ *
+ * @see https://jasmine.github.io/2.0/introduction.html#section-Spies:_%3Ccode%3EcreateSpyObj%3C/code%3E
+ * @param {string} baseName Human-readable name of the object. This is used for reporting purposes.
+ * @param methods {string[]} List of method names that will be added to the spy object.
+ */
+export function createSpyObj(baseName, methods) {
+  const obj = {};
+  methods.forEach(method => {
+    obj[method] = jest.fn().mockName(`${baseName}#${method}`);
+  });
+  return obj;
+}

spec/frontend/helpers/timeout.js

 const NS_PER_SEC = 1e9;
 const NS_PER_MS = 1e6;
+const IS_DEBUGGING = process.execArgv.join(' ').includes('--inspect-brk');
 
 let testTimeoutNS;
 
@@ -8,6 +9,13 @@ export const setTestTimeout = newTimeoutMS => {
   jest.setTimeout(newTimeoutMS);
 };
 
+// Allows slow tests to set their own timeout.
+// Useful for tests with jQuery, which is very slow in big DOMs.
+let temporaryTimeoutNS = null;
+export const setTestTimeoutOnce = newTimeoutMS => {
+  temporaryTimeoutNS = newTimeoutMS * NS_PER_MS;
+};
+
 export const initializeTestTimeout = defaultTimeoutMS => {
   setTestTimeout(defaultTimeoutMS);
 
@@ -19,12 +27,20 @@ export const initializeTestTimeout = defaultTimeoutMS => {
   });
 
   afterEach(() => {
+    let timeoutNS = testTimeoutNS;
+    if (Number.isFinite(temporaryTimeoutNS)) {
+      timeoutNS = temporaryTimeoutNS;
+      temporaryTimeoutNS = null;
+    }
+
     const [seconds, remainingNs] = process.hrtime(testStartTime);
     const elapsedNS = seconds * NS_PER_SEC + remainingNs;
 
-    if (elapsedNS > testTimeoutNS) {
+    // Disable the timeout error when debugging. It is meaningless because
+    // debugging always takes longer than the test timeout.
+    if (elapsedNS > timeoutNS && !IS_DEBUGGING) {
       throw new Error(
-        `Test took too long (${elapsedNS / NS_PER_MS}ms > ${testTimeoutNS / NS_PER_MS}ms)!`,
+        `Test took too long (${elapsedNS / NS_PER_MS}ms > ${timeoutNS / NS_PER_MS}ms)!`,
       );
     }
   });