Merge branch 'winh-timeline-entry-jest' into 'master'

Migrate timeline_entry_item_spec.js to Jest

See merge request gitlab-org/gitlab-ce!23686

jest.config.js

@@ -14,6 +14,7 @@ if (process.env.CI) {
 // eslint-disable-next-line import/no-commonjs
 module.exports = {
   testMatch: ['<rootDir>/spec/frontend/**/*_spec.js'],
+  moduleFileExtensions: ['js', 'json', 'vue'],
   moduleNameMapper: {
     '^~(.*)$': '<rootDir>/app/assets/javascripts$1',
     '^helpers(.*)$': '<rootDir>/spec/frontend/helpers$1',
@@ -26,4 +27,8 @@ module.exports = {
   reporters,
   setupTestFrameworkScriptFile: '<rootDir>/spec/frontend/test_setup.js',
   restoreMocks: true,
+  transform: {
+    '^.+\\.js$': 'babel-jest',
+    '^.+\\.vue$': 'vue-jest',
+  },
 };

package.json

@@ -157,6 +157,7 @@
     "karma-webpack": "^4.0.0-beta.0",
     "nodemon": "^1.18.4",
     "prettier": "1.15.2",
+    "vue-jest": "^3.0.1",
     "webpack-dev-server": "^3.1.10"
   }
 }

spec/frontend/dummy_spec.js

-it('does nothing', () => {});