Add setTestTimeout for Jest tests

Allows contributors to set the timeout
for individual jest tests.

spec/frontend/helpers/timeout.js

+let testTimeoutInMs;
+
+export const setTestTimeout = newTimeoutInMs => {
+  testTimeoutInMs = newTimeoutInMs;
+  jest.setTimeout(newTimeoutInMs);
+};
+
+export const initializeTestTimeout = defaultTimeoutInMs => {
+  setTestTimeout(defaultTimeoutInMs);
+
+  let testStartTime;
+
+  // https://github.com/facebook/jest/issues/6947
+  beforeEach(() => {
+    testStartTime = Date.now();
+  });
+
+  afterEach(() => {
+    const elapsedTimeInMs = Date.now() - testStartTime;
+    if (elapsedTimeInMs > testTimeoutInMs) {
+      throw new Error(`Test took too long (${elapsedTimeInMs}ms > ${testTimeoutInMs}ms)!`);
+    }
+  });
+};

spec/frontend/test_setup.js

 import Vue from 'vue';
 import Translate from '~/vue_shared/translate';
 import axios from '~/lib/utils/axios_utils';
+import { initializeTestTimeout } from './helpers/timeout';
 
-const testTimeoutInMs = 300;
-jest.setTimeout(testTimeoutInMs);
-
-let testStartTime;
-
-// https://github.com/facebook/jest/issues/6947
-beforeEach(() => {
-  testStartTime = Date.now();
-});
-
-afterEach(() => {
-  const elapsedTimeInMs = Date.now() - testStartTime;
-  if (elapsedTimeInMs > testTimeoutInMs) {
-    throw new Error(`Test took too long (${elapsedTimeInMs}ms > ${testTimeoutInMs}ms)!`);
-  }
-});
+initializeTestTimeout(300);
 
 // fail tests for unmocked requests
 beforeEach(done => {