docs: salvage HarmonyOS ArkTS guidance

rules/arkts/testing.md

@@ -0,0 +1,126 @@
+---
+paths:
+  - "**/*.ets"
+  - "**/*.ts"
+  - "**/ohosTest/**"
+---
+# HarmonyOS / ArkTS Testing
+
+> This file extends [common/testing.md](../common/testing.md) with HarmonyOS-specific testing practices.
+
+## Test Framework
+
+HarmonyOS uses the built-in test framework with `@ohos.test` capabilities:
+
+- **Unit tests**: Located in `src/ohosTest/ets/test/`
+- **UI tests**: Use `@ohos.UiTest` for component testing
+- **Instrument tests**: Run on device/emulator
+
+## Test Directory Structure
+
+```
+module/
+  |-- src/
+  |   |-- main/ets/          # Production code
+  |   |-- ohosTest/ets/      # Test code
+  |       |-- test/
+  |       |   |-- Ability.test.ets
+  |       |   |-- List.test.ets
+  |       |-- TestAbility.ets
+  |       |-- TestRunner.ets
+```
+
+## Running Tests
+
+```bash
+# Run all tests for a module
+hvigorw testHap -p product=default
+
+# Run tests on connected device
+hdc shell aa test -b com.example.app -m entry_test -s unittest /ets/TestRunner/OpenHarmonyTestRunner
+```
+
+## Unit Test Example
+
+```typescript
+import { describe, it, expect } from '@ohos/hypium';
+
+export default function UserViewModelTest() {
+  describe('UserViewModel', () => {
+    it('should_initialize_with_empty_state', 0, () => {
+      const vm = new UserViewModel();
+      expect(vm.userName).assertEqual('');
+      expect(vm.isLoading).assertFalse();
+    });
+
+    it('should_update_user_name', 0, () => {
+      const vm = new UserViewModel();
+      vm.updateUserName('Alice');
+      expect(vm.userName).assertEqual('Alice');
+    });
+
+    it('should_handle_empty_input', 0, () => {
+      const vm = new UserViewModel();
+      vm.updateUserName('');
+      expect(vm.userName).assertEqual('');
+      expect(vm.hasError).assertFalse();
+    });
+  });
+}
+```
+
+## UI Test Example
+
+```typescript
+import { describe, it, expect } from '@ohos/hypium';
+import { Driver, ON } from '@ohos.UiTest';
+
+export default function HomePageUITest() {
+  describe('HomePage_UI', () => {
+    it('should_display_title', 0, async () => {
+      const driver = Driver.create();
+      await driver.delayMs(1000);
+
+      const title = await driver.findComponent(ON.text('Home'));
+      expect(title !== null).assertTrue();
+    });
+
+    it('should_navigate_to_detail_on_click', 0, async () => {
+      const driver = Driver.create();
+      const button = await driver.findComponent(ON.id('detailButton'));
+      await button.click();
+      await driver.delayMs(500);
+
+      const detailTitle = await driver.findComponent(ON.text('Detail'));
+      expect(detailTitle !== null).assertTrue();
+    });
+  });
+}
+```
+
+## TDD Workflow for HarmonyOS
+
+Follow the standard TDD cycle adapted for HarmonyOS:
+
+1. **RED**: Write a failing test in `ohosTest/ets/test/`
+2. **GREEN**: Implement minimal code in `main/ets/` to pass
+3. **REFACTOR**: Clean up while keeping tests green
+4. **BUILD**: Run `hvigorw assembleHap` to verify compilation
+5. **VERIFY**: Run tests on device/emulator
+
+## Test Coverage Requirements
+
+- Minimum 80% coverage for all critical application code (ViewModels, services, utilities)
+- **Unit tests**: All utility functions, ViewModel logic, data models
+- **Integration tests**: API calls, database operations, cross-module interactions
+- **E2E / UI tests**: Critical user flows (login, navigation, data submission)
+- Test edge cases: empty data, network errors, permission denials
+
+## Testing Best Practices
+
+- Keep tests independent - no shared mutable state between tests
+- Mock network calls and system APIs in unit tests
+- Use meaningful test names: `should_[expected_behavior]_when_[condition]`
+- Test V2 state management reactivity: verify `@Trace` properties trigger UI updates
+- Test Navigation flows: verify `NavPathStack` push/pop/replace operations
+- Avoid testing framework internals - focus on business logic and user-visible behavior