chore: add basic test suite for hooks

.github/workflows/validate-js.yml

@@ -104,3 +104,30 @@ jobs:
 
     - name: Verify no files have changed after auto-fix
       run: git diff --exit-code HEAD
+
+  test:
+    name: Test JS
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Get yarn cache directory path
+      id: yarn-cache-dir-path
+      run: echo "::set-output name=dir::$(yarn cache dir)"
+    - name: Restore node_modules from cache
+      uses: actions/cache@v2
+      id: yarn-cache
+      with:
+        path: ${{ steps.yarn-cache-dir-path.outputs.dir }}
+        key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
+        restore-keys: |
+          ${{ runner.os }}-yarn-
+
+    - name: Install node_modules
+      run: yarn install --frozen-lockfile
+
+    - name: Install node_modules (example/)
+      run: yarn install --frozen-lockfile --cwd example
+
+    - name: Run Jest
+      run: yarn test

babel.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  presets: ['module:metro-react-native-babel-preset'],
+};

package.json

@@ -33,6 +33,7 @@
     "lint": "eslint \"**/*.{js,ts,tsx}\"",
     "lint-ci": "yarn lint -f ./node_modules/@firmnav/eslint-github-actions-formatter/dist/formatter.js",
     "lint-cpp": "scripts/clang-format.sh",
+    "test": "jest",
     "prepare": "git submodule update --init --recursive && bob build",
     "prepack": "bob build",
     "update-submodule": "git submodule update --remote --merge",
@@ -61,16 +62,22 @@
     "@react-native-community/eslint-config": "^3.2.0",
     "@react-native-community/eslint-plugin": "^1.3.0",
     "@release-it/conventional-changelog": "^5.1.1",
+    "@testing-library/react-native": "^12.3.2",
     "@tsconfig/react-native": "^2.0.3",
+    "@types/jest": "^29.5.7",
     "@types/react": "^18.0.34",
+    "@types/react-test-renderer": "^18.0.5",
     "@typescript-eslint/eslint-plugin": "^5.58.0",
     "@typescript-eslint/parser": "^5.58.0",
     "eslint": "^8.38.0",
     "eslint-plugin-jest": "^27.2.1",
+    "jest": "^29.7.0",
+    "metro-react-native-babel-preset": "^0.77.0",
     "prettier": "^2.8.7",
     "react": "^18.2.0",
     "react-native": "^0.71.6",
     "react-native-builder-bob": "^0.20.4",
+    "react-test-renderer": "^18.2.0",
     "release-it": "^15.10.1",
     "typescript": "^4.9.4"
   },

test/hooks.test.tsx

@@ -0,0 +1,88 @@
+import React from 'react';
+import { Button, Text } from 'react-native';
+import {
+  act,
+  fireEvent,
+  render,
+  renderHook,
+  screen,
+} from '@testing-library/react-native';
+import { MMKV, useMMKVNumber, useMMKVString } from '../src';
+
+const mmkv = new MMKV();
+
+beforeEach(() => {
+  mmkv.clearAll();
+});
+
+test('hooks update when the value is changed directly through the instance', () => {
+  const { result } = renderHook(() => useMMKVString('string-key', mmkv));
+
+  expect(result.current[0]).toBeUndefined();
+
+  // First, make a "normal" change
+  act(() => {
+    result.current[1]('value 1');
+  });
+
+  expect(result.current[0]).toStrictEqual('value 1');
+
+  // Now, make the change directly through the instance.
+  act(() => {
+    mmkv.set('string-key', 'value 2');
+  });
+  expect(result.current[0]).toStrictEqual('value 2');
+});
+
+test('functional updates to hooks', () => {
+  const Component: React.FC = () => {
+    const [state, setState] = React.useState(0);
+    const [value, setValue] = useMMKVNumber('number-key', mmkv);
+
+    return (
+      <>
+        <Button
+          testID="button"
+          title="Double Increment Me"
+          onPress={() => {
+            // Increment the state value twice, using the function form of useState.
+            setState((current) => current + 1);
+            setState((current) => current + 1);
+
+            // Increment the MMKV value twice, using the same function form.
+            setValue((current) => (current ?? 0) + 1);
+            setValue((current) => (current ?? 0) + 1);
+          }}
+        />
+        <Text testID="state-value">State: {state.toString()}</Text>
+        <Text testID="mmkv-value">MMKV: {(value ?? 0).toString()}</Text>
+      </>
+    );
+  };
+
+  render(<Component />);
+
+  const button = screen.getByTestId('button');
+
+  // Why these assertions:
+  // https://github.com/mrousavy/react-native-mmkv/issues/599
+  fireEvent.press(button);
+  expect(screen.getByTestId('state-value').children).toStrictEqual([
+    'State: ',
+    '2',
+  ]);
+  expect(screen.getByTestId('mmkv-value').children).toStrictEqual([
+    'MMKV: ',
+    '2',
+  ]);
+
+  fireEvent.press(button);
+  expect(screen.getByTestId('state-value').children).toStrictEqual([
+    'State: ',
+    '4',
+  ]);
+  expect(screen.getByTestId('mmkv-value').children).toStrictEqual([
+    'MMKV: ',
+    '4',
+  ]);
+});