Set up Jest testing framework

Author: jahn96

.eslintignore

@@ -3,4 +3,4 @@ dist
 coverage
 **/*.d.ts
 tests
-_temp_extension
+_temp_extension

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

@@ -75,6 +75,7 @@
     "eslint-plugin-prettier": "^3.1.2",
     "eslint-plugin-react": "^7.20.4",
     "husky": "^4.2.5",
+    "jest": "^24",
     "lint-staged": "^10.2.13",
     "mkdirp": "^1.0.3",
     "npm-run-all": "^4.1.5",

test/test.spec.ts

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

tsconfig.test.json

@@ -0,0 +1,26 @@
+{
+    "compilerOptions": {
+      "declaration": true,
+      "noImplicitAny": true,
+      "noEmitOnError": true,
+      "noUnusedLocals": true,
+      "module": "commonjs",
+      "moduleResolution": "node",
+      "target": "es2015",
+      "outDir": "lib",
+      "lib": [
+        "es2015",
+        "es2015.collection",
+        "dom",
+        "es2015.iterable",
+        "es2017.object"
+      ],
+      "types": ["jest", "node"],
+      "jsx": "react",
+      "resolveJsonModule": true,
+      "esModuleInterop": true,
+      "strictNullChecks": true,
+      "skipLibCheck": true
+    },
+    "include": ["src/*", "test/*"]
+  }