Set up Jest testing framework

Author: jahn96

.eslintignore

@@ -3,4 +3,6 @@ dist
 coverage
 **/*.d.ts
 test
-_temp_extension
+_temp_extension
+babel.config.ts
+jest.config.ts

babel.config.ts

@@ -0,0 +1,12 @@
+module.exports = {
+  presets: [
+    [
+      '@babel/preset-env',
+      {
+        targets: {
+          node: 'current'
+        }
+      }
+    ]
+  ]
+};

jest.config.ts

@@ -0,0 +1,20 @@
+import path = require('path');
+
+const config = function(baseDir: string) {
+  return {
+    preset: 'ts-jest/presets/js-with-babel',
+    moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json', 'node'],
+    transformIgnorePatterns: ['/node_modules/(?!(@jupyterlab/.*)/)'],
+    reporters: ['default', 'jest-junit', 'jest-summary-reporter'],
+    coverageReporters: ['json', 'lcov', 'text', 'html'],
+    coverageDirectory: path.join(baseDir, 'coverage'),
+    testRegex: '/test/.*.ts[x]?$',
+    globals: {
+      'ts-jest': {
+        tsConfig: 'tsconfig.test.json'
+      }
+    }
+  };
+};
+
+module.exports = config(__dirname);

package.json

@@ -44,7 +44,9 @@
     "prepare": "jlpm run clean && jlpm run build:prod",
     "watch": "run-p watch:src watch:labextension",
     "watch:labextension": "jupyter labextension watch .",
-    "watch:src": "tsc -w"
+    "watch:src": "tsc -w",
+    "test": "jest",
+    "test:cov": "jest --collect-coverage"
   },
   "dependencies": {
     "@jupyterlab/application": "^3.0.3",
@@ -71,6 +73,9 @@
     "@typescript-eslint/eslint-plugin": "^2.27.0",
     "@typescript-eslint/parser": "^2.27.0",
     "eslint": "^7.5.0",
+    "@babel/core": "^7",
+    "@babel/preset-env": "^7",
+    "@types/jest": "^24",
     "eslint-config-prettier": "^6.10.1",
     "eslint-plugin-prettier": "^3.1.2",
     "eslint-plugin-react": "^7.20.4",
@@ -82,7 +87,8 @@
     "npm-run-all": "^4.1.5",
     "prettier": "^1.19.0",
     "rimraf": "^3.0.2",
-    "typescript": "~4.1.3"
+    "typescript": "~4.1.3",
+    "ts-jest": "^24"
   },
   "sideEffects": [
     "style/*.css",

test/test.spec.ts

@@ -0,0 +1,3 @@
+test('two plus two is four', () => {
+  expect(2 + 2).toBe(4);
+});

tsconfig.test.json

@@ -15,7 +15,7 @@
         "es2015.iterable",
         "es2017.object"
       ],
-      "types": ["jest"],
+      "types": ["jest", "node"],
       "typeRoots": ["./types", "./node_modules/@types"],
       "jsx": "react",
       "resolveJsonModule": true,