Created README file for test folder with clear instruction on required packages and test enviroment setup and testing instruction

Author: xueapp

__tests__/Readme.md

@@ -0,0 +1,62 @@
+# Testing 
+
+### Preparation
+
+1. React Testing Library versions 13+ require React v18. If your project uses an older version of React, be sure to install version 12
+```
+npm install --save-dev @testing-library/react@12
+
+``` 
+2. install additional packages
+```
+npm install -g jest
+npm i @jest/types
+npm i ts-jest
+npm i jest-environment-jsdom
+npm i --save-dev @types/jest
+npm i @types/node
+```
+3. create jest.config.js 
+```
+module.exports = {
+  verbose: true,
+  setupFilesAfterEnv: ['./jest_setup/windowMock.js'],
+  testEnvironment: "jsdom",
+  preset: 'ts-jest/presets/js-with-ts',
+  moduleNameMapper: {
+    '\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$':
+      '<rootDir>/jest_setup/fileMock.js',
+    '\\.(css|less|scss)$': '<rootDir>/jest_setup/styleMock.js',
+  },
+  collectCoverage: true,
+  types: ["jest","node"],
+};
+```
+4. make sure jest_setup folder is at root directory of Chronos with styleMock.js and windowMock.js
+
+  styleMock.js
+  ```
+  module.exports = {};
+  ```
+  windowMock.js
+  ```
+  // Mock window environment
+  window.require = require;
+
+  // Mock import statements for Plotly
+  window.URL.createObjectURL = () => {};
+
+  // Mock get context
+  HTMLCanvasElement.prototype.getContext = () => {};
+  ```
+5. use `npm run test` to run jest tests
+
+### Contributing
+
+Chronos hopes to inspire an active community of both users and developers. For questions, comments, or contributions, please submit a pull request.
+
+### People
+[Snow X. Bai](https://github.com/xueapp)
+[Taylor Zhang](https://github.com/taylrzhang)
+[Tim Lee](https://github.com/timlee12)
+[Roberto Meloni](https://github.com/RobertoRueMeloni)

jest.config.js

@@ -1,11 +1,13 @@
 module.exports = {
   verbose: true,
   setupFilesAfterEnv: ['./jest_setup/windowMock.js'],
+  testEnvironment: "jsdom",
   preset: 'ts-jest/presets/js-with-ts',
   moduleNameMapper: {
     '\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$':
       '<rootDir>/jest_setup/fileMock.js',
     '\\.(css|less|scss)$': '<rootDir>/jest_setup/styleMock.js',
   },
   collectCoverage: true,
+  types: ["jest","node"],
 };