Unit Testing Ionic project with Jest

Install jest and other packages, in my case I had Jest 26.6 installed :

npm i jest @types/jest ts-jest typescript -D

If your package.json file contains "type": "module", [which causes Node to assume modules are in es6 format, you may have to remove that line].

Create a jest.config.js in the root folder ( you could create a config file like so npx jest –init but the default generated did not work for me.):

module.exports = {
  "roots": [
    "./src/app/services"
  ],
  "testMatch": [
    "**/__tests__/**/.+(ts|tsx|js)", 
    "**/?(*.)+(spec|test).+(ts|tsx|js)"
  ],
  "transform": {
    "^.+\\.(ts|tsx)$": "ts-jest"
  },
}