Create mock_just_audio_platform.dart

Author: Cirrus CI

packages/fwfh_just_audio/copilot_002.md

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+# Copilot Session 002: Modernizing Just Audio Mock Platform
+
+## Session Overview
+This session focused on refactoring the test mock implementation for the fwfh_just_audio package to use the modern `Fake` pattern from test_api, aligning with the patterns used in other packages within the workspace.
+
+## Problem Statement
+The existing `audio_player_test.dart` file was directly extending `JustAudioPlatform` and `AudioPlayerPlatform` classes to create mock implementations. This approach was outdated compared to the newer `Fake` mechanism used in other packages like `fwfh_chewie` and `fwfh_webview`.
+
+## Key Changes Made
+
+### 1. Created `mock_just_audio_platform.dart`
+- **Location**: `./packages/fwfh_just_audio/test/mock_just_audio_platform.dart`
+- **Pattern**: Used `Fake` with `MockPlatformInterfaceMixin` following the same pattern as:
+  - `./packages/fwfh_chewie/test/mock_video_player_platform.dart`
+  - `./packages/fwfh_webview/test/mock_webview_platform.dart`
+
+**Key features of the new mock**:
+```dart
+class _FakeJustAudioPlatform extends Fake
+    with MockPlatformInterfaceMixin
+    implements JustAudioPlatform
+
+class _FakeAudioPlayerPlatform extends Fake implements AudioPlayerPlatform
+```
+
+- Exported global variables for test state management:
+  - `commands` - tracks platform method calls
+  - `duration` - configurable audio duration
+  - `playbackEvents` - stream controller for playback events
+
+- Provided setup/teardown functions:
+  - `mockJustAudioPlatform()` - initializes the mock platform
+  - `initializeMockPlatform()` - resets state for each test
+  - `disposeMockPlatform()` - cleans up resources
+
+### 2. Updated `audio_player_test.dart`
+- **Removed**: Direct class extensions (`_JustAudioPlatform`, `_AudioPlayerPlatform`)
+- **Removed**: Private variables (`_commands`, `_duration`, `_playbackEvents`)
+- **Added**: Import for the new mock platform
+- **Updated**: All test code to use public exports from mock platform
+- **Fixed**: `CommandType` enum usage (made public instead of private `_CommandType`)
+
+### 3. Critical Bug Fixes
+- **Added missing `playerDataMessageStream`**: The newer just_audio version requires this stream property
+- **Maintained command tracking**: All platform method calls are properly tracked for test assertions
+- **Preserved test behavior**: All existing tests continue to pass with identical behavior
+
+## Technical Details
+
+### Mock Platform Implementation
+The mock implements all required platform interface methods:
+- `load()` - tracks load commands and simulates loading/ready states
+- `play()`, `pause()` - tracks playback commands
+- `setVolume()` - tracks volume changes
+- `seek()` - tracks seek operations
+- Plus all other required platform methods with no-op implementations
+
+### Stream Management
+- `playbackEventMessageStream` - provides playback state events
+- `playerDataMessageStream` - required by newer just_audio versions (returns empty stream)
+
+### Command Tracking
+Uses `Tuple2<CommandType, dynamic>` to track:
+- `CommandType.load` - audio loading operations
+- `CommandType.play` - play commands
+- `CommandType.pause` - pause commands
+- `CommandType.setVolume` - volume changes
+- `CommandType.seek` - seek operations
+
+## Benefits of the Refactor
+
+1. **Consistency**: Now follows the same mock pattern as other packages in the workspace
+2. **Maintainability**: Cleaner separation of concerns with dedicated mock file
+3. **Modern Approach**: Uses `Fake` pattern instead of direct class extension
+4. **Better Testing**: Proper `MockPlatformInterfaceMixin` integration
+5. **Future-Proof**: Easier to extend and maintain as platform interfaces evolve
+
+## Test Results
+All tests pass successfully:
+- ✅ plays then pauses on completion
+- ✅ shows remaining (narrow)
+- ✅ shows position & duration (wide)
+- ✅ seeks
+- ✅ mute functionality tests
+- ✅ screenshot/golden tests
+
+## Files Modified
+1. **Created**: `./packages/fwfh_just_audio/test/mock_just_audio_platform.dart`
+2. **Modified**: `./packages/fwfh_just_audio/test/audio_player_test.dart`
+
+## Lessons Learned
+- The `playerDataMessageStream` is a newer requirement in just_audio platform interface
+- Command execution order can vary between different platform implementations
+- Using `Fake` with `MockPlatformInterfaceMixin` provides better mock behavior than direct extension
+- Global state management in test mocks requires careful setup/teardown handling
+
+## Next Steps
+This refactor provides a solid foundation for:
+- Adding new test cases
+- Updating to newer just_audio versions
+- Maintaining consistency across the workspace's test patterns