[Sub] Write API Client Unit Tests

[switch180]

Parent Issue: #4 Zero Test Coverage

Objective

Create comprehensive unit tests for the RiverLinkApiClient class covering connection management, command execution, and error handling.

Test Coverage Areas

Connection Tests

• test_connect_success - Successful connection
• test_connect_failure - Connection errors
• test_disconnect - Clean disconnection
• test_reconnect_after_failure - Auto-reconnect logic

Command Tests

• test_send_command_success - Successful command execution
• test_send_command_processing - PROCESSING status handling
• test_poll_request - Async operation polling
• test_command_timeout - Timeout handling

API Method Tests

• test_async_get_data - Device data retrieval
• test_async_join_subscription - Video routing
• test_async_leave_subscription - Disconnect
• test_async_set_video_mode - Display mode changes

Error Handling Tests

• test_connection_error - RiverLinkApiClientConnectionError
• test_communication_error - RiverLinkApiClientCommunicationError
• test_invalid_response - Malformed JSON handling
• test_api_error_response - API error responses

Mock Strategy

# Mock asyncio.open_connection
@pytest.fixture
def mock_connection():
    reader = AsyncMock(spec=asyncio.StreamReader)
    writer = AsyncMock(spec=asyncio.StreamWriter)
    return reader, writer

Target Coverage

• Goal: 90%+ line coverage for api.py
• Focus: Critical paths and error scenarios

References

• File: custom_components/riverlink/api.py
• Parent Issue: Zero Test Coverage - Critical Testing Infrastructure Gap #4
• Related: Issue [Sub] Set up Test Infrastructure with pytest-homeassistant-custom-component #14 (Test infrastructure)

Priority

🔴 High - Core functionality