Add helpers for HTML fixtures to Jest

spec/frontend/helpers/fixtures.js

-/* eslint-disable import/prefer-default-export, global-require, import/no-dynamic-require */
-
 import fs from 'fs';
 import path from 'path';
 
@@ -7,16 +5,32 @@ import { ErrorWithStack } from 'jest-util';
 
 const fixturesBasePath = path.join(process.cwd(), 'spec', 'javascripts', 'fixtures');
 
-export function getJSONFixture(relativePath, ee = false) {
-  const absolutePath = path.join(fixturesBasePath, ee ? 'ee' : '', relativePath);
+export function getFixture(relativePath) {
+  const absolutePath = path.join(fixturesBasePath, relativePath);
   if (!fs.existsSync(absolutePath)) {
     throw new ErrorWithStack(
       `Fixture file ${relativePath} does not exist.
 
 Did you run bin/rake karma:fixtures?`,
-      getJSONFixture,
+      getFixture,
     );
   }
 
-  return require(absolutePath);
+  return fs.readFileSync(absolutePath, 'utf8');
 }
+
+export const getJSONFixture = relativePath => JSON.parse(getFixture(relativePath));
+
+export const resetHTMLFixture = () => {
+  document.body.textContent = '';
+};
+
+export const setHTMLFixture = (htmlContent, resetHook = afterEach) => {
+  document.body.outerHTML = htmlContent;
+  resetHook(resetHTMLFixture);
+};
+
+export const loadHTMLFixture = (relativePath, resetHook = afterEach) => {
+  const fileContent = getFixture(relativePath);
+  setHTMLFixture(fileContent, resetHook);
+};