setup testing with jest

jest.config.js

@@ -0,0 +1,4 @@
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+};

package.json

@@ -19,6 +19,7 @@
     "lint:eslint:fix": "yarn eslint --fix",
     "lint:prettier": "yarn prettier --check src",
     "lint:prettier:fix": "yarn prettier --check --write src",
+    "test": "yarn jest",
     "start": "node build/src/index.js",
     "start:dev": "yarn build:ts && yarn start"
   },
@@ -64,6 +65,7 @@
     "@types/fs-extra": "^9.0.6",
     "@types/iarna__toml": "^2.0.1",
     "@types/inquirer": "^7.3.1",
+    "@types/jest": "^26.0.20",
     "@types/node": "^14.14.25",
     "eslint": "^7.19.0",
     "eslint-config-airbnb-typescript": "^12.0.0",
@@ -71,7 +73,9 @@
     "eslint-plugin-import": "^2.22.1",
     "eslint-plugin-prettier": "^3.3.1",
     "husky": "^4.3.8",
+    "jest": "^26.6.3",
     "prettier": "^2.2.1",
+    "ts-jest": "^26.5.1",
     "ts-node": "^9.1.1",
     "typescript": "^4.1.3"
   }