[Sub] Write Integration Tests

[switch180]

Parent Issue: #4 Zero Test Coverage

Objective

Create end-to-end integration tests covering the full setup flow, coordinator updates, and user actions with mocked API.

Test Coverage Areas

Setup Flow Tests

• test_setup_entry_success - Successful integration setup
• test_setup_entry_failure - Connection failure handling
• test_config_flow_user_step - UI configuration
• test_config_flow_validation - Connection validation
• test_platform_loading - All platforms load correctly

Coordinator Integration Tests

• test_coordinator_first_refresh - Initial data fetch
• test_coordinator_update_cycle - Polling updates
• test_coordinator_update_failure - Error recovery
• test_entity_creation - Entities created from data

User Action Integration Tests

• test_video_routing_flow - Complete routing scenario
• test_display_mode_change_flow - Mode change + refresh
• test_resolution_change_flow - Resolution update
• test_disconnect_flow - Leave subscription flow

State Propagation Tests

• test_api_to_coordinator_to_entity - Full data flow
• test_entity_state_update - State updates on refresh
• test_multiple_entities_update - All entities sync

Error Scenario Tests

• test_network_failure_recovery - Transient errors
• test_device_disconnect_handling - Device offline
• test_api_error_propagation - Error handling

Test Strategy

# Use Home Assistant test utilities
from pytest_homeassistant_custom_component.common import MockConfigEntry

async def test_setup_entry_success(hass):
    entry = MockConfigEntry(
        domain=DOMAIN,
        data={"host": "10.0.1.135", "port": 6970}
    )
    # Mock API responses
    # Test full setup

Target Coverage

• Goal: 75%+ coverage for integration scenarios
• Focus: Critical user flows and error paths

References

• Files: __init__.py, config_flow.py
• Parent Issue: Zero Test Coverage - Critical Testing Infrastructure Gap #4
• Depends on: Issues [Sub] Set up Test Infrastructure with pytest-homeassistant-custom-component #14, [Sub] Write API Client Unit Tests #15, [Sub] Write Coordinator Unit Tests #16, [Sub] Write Entity Platform Tests #17

Priority

🟡 Medium - Integration validation