Added unit tests

.gitignore

@@ -5,5 +5,4 @@ docs/build
 docs/src/hooks
 docs/blog
 dist
-example
-test
+example

package.json

@@ -54,11 +54,15 @@
   ],
   "devDependencies": {
     "@size-limit/preset-small-lib": "^7.0.8",
+    "@testing-library/jest-dom": "^5.16.2",
+    "@testing-library/react-hooks": "^7.0.2",
+    "@types/jest": "^27.4.1",
     "@types/react": "^17.0.39",
     "@types/react-dom": "^17.0.11",
     "husky": "^7.0.4",
     "react": "^17.0.2",
     "react-dom": "^17.0.2",
+    "react-test-renderer": "^17.0.2",
     "size-limit": "^7.0.8",
     "tsdx": "^0.14.1",
     "tslib": "^2.3.1",

test/useLegacyState.test.ts

@@ -0,0 +1,29 @@
+import { renderHook, act } from '@testing-library/react-hooks';
+import { useLegacyState } from '../src';
+
+const initialState = {
+  firstName: 'John',
+};
+
+describe('useLegacyState', () => {
+  it('should return correct initial state', () => {
+    const hook = renderHook(() => useLegacyState(initialState));
+    expect(hook.result.current[0]).toStrictEqual(initialState);
+  });
+
+  it('should return the updated state after setState', () => {
+    const hook = renderHook(() => useLegacyState(initialState));
+    act(() => hook.result.current[1]({ lastName: 'Doe' }));
+    expect(hook.result.current[0]).toStrictEqual({
+      ...initialState,
+      lastName: 'Doe',
+    });
+
+    act(() => hook.result.current[1]({ age: 32 }));
+    expect(hook.result.current[0]).toStrictEqual({
+      ...initialState,
+      lastName: 'Doe',
+      age: 32,
+    });
+  });
+});