#4: Set up and maintain tests for the web app

 - removed hidden errors for Snippet-rendering

src/jest.config.js

@@ -2,6 +2,9 @@ console.log('Jest Config Loaded: maa-client/src/jest.config.js');
 console.log('JEST_JUNIT_OUTPUT_DIR=', process.env.JEST_JUNIT_OUTPUT_DIR);
 
 module.exports = {
+  setupFiles: [
+    '<rootDir>/window.setup.js'
+  ],
   moduleNameMapper:{
     "\\.(css|less|sass|scss)$": "<rootDir>/__mocks__/styleMock.js",
     "\\.(gif|ttf|eot|svg)$": "<rootDir>/__mocks__/fileMock.js"

src/ui/elements/Snippet/Snippet.test.js

@@ -6,6 +6,29 @@ import { history, store } from '../../../app/store';
 import { ConnectedRouter } from 'connected-react-router';
 import { Snippet } from './index';
 
+// from: https://github.com/popperjs/popper-core/issues/478
+// How to use Popper.js in Jest / JSDOM?
+jest.mock(
+  'popper.js',
+  () =>
+    class Popper {
+      static placements = [
+        'auto', 'auto-end', 'auto-start',
+        'bottom', 'bottom-end', 'bottom-start',
+        'left', 'left-end', 'left-start',
+        'right', 'right-end', 'right-start',
+        'top', 'top-end', 'top-start'
+      ];
+
+      constructor() {
+        return {
+          destroy: () => {},
+          scheduleUpdate: () => {}
+        };
+      }
+    }
+);
+
 describe(`src/ui/elements/Snippet/index.js`, () => {
   describe(`Snippet component`, () => {
 

src/window.setup.js

@@ -0,0 +1,5 @@
+console.log('src/window.setup.js');
+
+window.scrollTo = jest.fn();
+window.prompt = jest.fn();
+window.alert = jest.fn();