Added Jest

package.json

@@ -9,7 +9,8 @@
   "private": false,
   "scripts": {
     "check-types": "tsc",
-    "start": "webpack-dev-server --mode development"
+    "start": "webpack-dev-server --mode development",
+    "test": "jest"
   },
   "devDependencies": {
     "@babel/core": "^7.4.3",
@@ -18,11 +19,15 @@
     "@babel/preset-env": "^7.4.3",
     "@babel/preset-react": "^7.0.0",
     "@babel/preset-typescript": "^7.3.3",
+    "@types/jest": "^24.0.11",
     "@types/node": "^11.13.0",
     "@types/react": "^16.8.12",
     "@types/react-dom": "^16.8.3",
     "babel-loader": "^8.0.5",
     "html-webpack-plugin": "^3.2.0",
+    "jest": "^24.7.1",
+    "react-testing-library": "^6.1.1",
+    "ts-jest": "^24.0.1",
     "typescript": "^3.4.1",
     "webpack": "^4.29.6",
     "webpack-cli": "^3.3.0",
@@ -31,5 +36,19 @@
   "dependencies": {
     "react": "^16.8.6",
     "react-dom": "^16.8.6"
+  },
+  "jest": {
+    "transform": {
+      ".(ts|tsx)": "ts-jest"
+    },
+    "testRegex": "(/__tests__/.*|\\.(test|spec))\\.(ts|tsx|js)$",
+    "moduleFileExtensions": [
+      "ts",
+      "tsx",
+      "js",
+      "jsx",
+      "json",
+      "node"
+    ]
   }
 }

src/__tests__/App.test.tsx

@@ -0,0 +1,15 @@
+import React from 'react'
+import { render } from 'react-testing-library'
+import App from '../App'
+
+describe('App component', () => {
+  it('should render', () => {
+    const component = render(<App />)
+    expect(component).toBeTruthy()
+  })
+
+  it('shoult match snapshot', () => {
+    const component = render(<App />)
+    expect(component.asFragment()).toMatchSnapshot()
+  })
+})

src/__tests__/__snapshots__/App.test.tsx.snap

@@ -0,0 +1,9 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`App component shoult match snapshot 1`] = `
+<DocumentFragment>
+  <h1>
+    React Stellar
+  </h1>
+</DocumentFragment>
+`;

tsconfig.json

@@ -2,7 +2,7 @@
   "compilerOptions": {
     "target": "esnext",
     "module": "esnext",
-    "jsx": "preserve",
+    "jsx": "react",
     "moduleResolution": "node",
     "allowJs": true,
     "noEmit": true,