chore(tooling): set up unit tests

Author: hydrosquall

.npmignore

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

jest.config.cjs

@@ -1,20 +1,27 @@
 {
   "scripts": {
     "build": "node_modules/.bin/esbuild --target=es2019 ./src/index.jsx --bundle --platform=node --outfile=index.js",
-    "prepare": "husky install"
+    "prepare": "husky install",
+    "test:jest": "jest",
+    "test:watch": "jest --watch",
+    "test:coverage": "jest --coverage",
+    "test": "npm run test:jest --"
   },
   "dependencies": {
     "@actions/core": "^1.4.0",
     "@actions/exec": "^1.1.0",
     "d3": "^7.0.0",
     "esbuild": "^0.12.15",
-    "husky": "^7.0.1",
     "lodash": "^4.17.21",
     "minimatch": "^3.0.4",
     "react": "^17.0.2",
     "react-dom": "^17.0.2"
   },
   "devDependencies": {
-    "husky": "^7.0.0"
+    "husky": "^7.0.0",
+    "@types/jest": "^27.0.1",
+    "jest": "^27.0.6",
+    "ts-jest": "^27.0.4",
+    "typescript": "^4.3.5"
   }
 }

package.json

@@ -0,0 +1,19 @@
+{
+  "compilerOptions": {
+    "target": "es5",
+    "module": "commonjs",                           /* Specify module code generation: 'none', 'commonjs', 'amd',
+
+    /* Strict Type-Checking Options */
+    "strict": true,                                 /* Enable all strict type-checking options. */
+    "noImplicitAny": true,                          /* Raise error on expressions and declarations with an implied 'any' type. */
+    "strictNullChecks": true,                       /* Enable strict null checks. */
+    "rootDirs": [
+      "src"
+    ],
+    "allowSyntheticDefaultImports": true,            /* Allow default imports from modules with no default export.
+    "esModuleInterop": true,                         /* Enables emit interoperability between CommonJS and ES
+    /* Advanced Options */
+    "skipLibCheck": true,                           /* Skip type checking of declaration files. */
+    "forceConsistentCasingInFileNames": true        /* Disallow inconsistently-cased references to the same file. */
+  }
+}