Add a basic unit test for demo example

.vscode/settings.json

@@ -0,0 +1,3 @@
+{
+    "deno.enable": false
+}

src/index.test.tsx

@@ -1,7 +1,93 @@
-import { ExampleComponent } from '.'
+import React from 'react';
+import { render, fireEvent } from '@testing-library/react';
+import '@testing-library/jest-dom/extend-expect';
+import { useUndo, useRedo, RecoilUndoRoot } from './index';
+import {
+  RecoilRoot,
+  atom,
+  selector,
+  useRecoilState,
+  useRecoilValue,
+} from 'recoil';
 
-describe('ExampleComponent', () => {
-  it('is truthy', () => {
-    expect(ExampleComponent).toBeTruthy()
-  })
-})
+const COUNT = atom({
+  default: 0,
+  key: 'count',
+});
+
+const TWO_TIMES = selector({
+  get: ({ get }) => get(COUNT) * 2,
+  key: 'two_times',
+});
+
+const App = () => {
+  return (
+    <RecoilRoot>
+      <RecoilUndoRoot trackedAtoms={[COUNT]}>
+        <Counter />
+      </RecoilUndoRoot>
+    </RecoilRoot>
+  );
+};
+
+function Counter() {
+  const [count, setCount] = useRecoilState(COUNT);
+  const double = useRecoilValue(TWO_TIMES);
+  const undo = useUndo();
+  const redo = useRedo();
+  return (
+    <div>
+      <div>
+        <button
+          data-testid='dec'
+          onClick={() => setCount((count) => count - 1)}
+        >
+          -
+        </button>
+        <span data-testid='count'>{count}</span>
+        <button
+          data-testid='inc'
+          onClick={() => setCount((count) => count + 1)}
+        >
+          +
+        </button>
+      </div>
+      <button data-testid='undo' onClick={undo}>
+        Undo
+      </button>
+      <button data-testid='redo' onClick={redo}>
+        Redo
+      </button>
+      <div>{double}</div>
+    </div>
+  );
+}
+
+describe('recoil-undo', () => {
+  it('handles a simple undo and redo case', () => {
+    const { getByTestId } = render(<App />);
+    const inc = getByTestId('inc');
+    const dec = getByTestId('dec');
+    const count = getByTestId('count');
+    const undoButton = getByTestId('undo');
+    const redoButton = getByTestId('redo');
+
+    const plus = () => fireEvent.click(inc);
+    const minus = () => fireEvent.click(dec);
+    const getCount = () => Number(count.textContent);
+    const undo = () => fireEvent.click(undoButton);
+    const redo = () => fireEvent.click(redoButton);
+
+    plus();
+    expect(getCount()).toBe(1);
+
+    plus();
+    plus();
+    minus();
+    expect(getCount()).toBe(2);
+    undo();
+    expect(getCount()).toBe(3);
+    redo();
+    expect(getCount()).toBe(2);
+  });
+});

src/react-app-env.d.ts

@@ -0,0 +1 @@
+/// <reference types="react-scripts" />

tsconfig.json

@@ -2,7 +2,10 @@
   "compilerOptions": {
     "outDir": "dist",
     "module": "esnext",
-    "lib": ["dom", "esnext"],
+    "lib": [
+      "dom",
+      "esnext"
+    ],
     "moduleResolution": "node",
     "jsx": "react",
     "sourceMap": true,
@@ -16,8 +19,22 @@
     "noUnusedLocals": true,
     "noUnusedParameters": true,
     "allowSyntheticDefaultImports": true,
-    "downlevelIteration": true
+    "downlevelIteration": true,
+    "target": "es5",
+    "allowJs": true,
+    "skipLibCheck": true,
+    "strict": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "noEmit": true
   },
-  "include": ["src"],
-  "exclude": ["node_modules", "dist", "example"]
+  "include": [
+    "src"
+  ],
+  "exclude": [
+    "node_modules",
+    "dist",
+    "example"
+  ]
 }