# Backend Tests - Developer Guide

## Overview

Comprehensive test suite for the Paper Dynasty backend game engine covering unit tests, integration tests, and end-to-end scenarios.

**Test Structure**:
```
tests/
├── unit/                       # Fast, isolated unit tests (no DB)
│   ├── config/                 # League configs, PlayOutcome enum
│   ├── core/                   # Game engine, dice, state manager, validators
│   ├── models/                 # Pydantic models (game, player, roster)
│   └── terminal_client/        # Terminal client modules
├── integration/                # Database-dependent tests
│   ├── database/               # DatabaseOperations tests
│   ├── test_game_engine.py     # Full game engine with DB
│   └── test_state_persistence.py  # State recovery tests
└── e2e/                        # End-to-end tests (future)
```

## Running Tests

### Unit Tests (Recommended)

**Fast, reliable, no database required**:
```bash
# All unit tests
pytest tests/unit/ -v

# Specific module
pytest tests/unit/core/test_game_engine.py -v

# Specific test
pytest tests/unit/core/test_game_engine.py::TestGameEngine::test_start_game -v

# With coverage
pytest tests/unit/ --cov=app --cov-report=html
```

**Unit tests should always pass**. If they don't, it's a real code issue.

### Integration Tests (Database Required)

**⚠️ CRITICAL: Integration tests have known infrastructure issues**

#### Known Issue: AsyncPG Connection Conflicts

**Problem**: Integration tests share database connections and event loops, causing:
- `asyncpg.exceptions._base.InterfaceError: cannot perform operation: another operation is in progress`
- `Task got Future attached to a different loop`

**Why This Happens**:
- AsyncPG connections don't support concurrent operations
- pytest-asyncio fixtures with mismatched scopes (module vs function)
- Tests running in parallel try to reuse the same connection

**Current Workaround**: Run integration tests **individually** or **serially**:

```bash
# Run one test at a time (always works)
pytest tests/integration/database/test_operations.py::TestDatabaseOperationsGame::test_create_game -v

# Run test class serially
pytest tests/integration/database/test_operations.py::TestDatabaseOperationsGame -v

# Run entire file (may have conflicts after first test)
pytest tests/integration/database/test_operations.py -v

# Force serial execution (slower but more reliable)
pytest tests/integration/ -v -x  # -x stops on first failure
```

**DO NOT**:
- Run all integration tests at once: `pytest tests/integration/ -v` ❌ (will fail)
- Expect integration tests to work in parallel ❌

**Long-term Fix Needed**:
1. Update fixtures to use proper asyncio scope management
2. Ensure each test gets isolated database session
3. Consider using `pytest-xdist` with proper worker isolation
4. Or redesign fixtures to create fresh connections per test

### All Tests

```bash
# Run everything (expect integration failures due to connection issues)
pytest tests/ -v

# Run with markers
pytest tests/ -v -m "not integration"  # Skip integration tests
pytest tests/ -v -m integration        # Only integration tests
```

## Test Configuration

### pytest.ini

```ini
[pytest]
asyncio_mode = auto
asyncio_default_fixture_loop_scope = function
testpaths = tests
python_files = test_*.py
python_classes = Test*
python_functions = test_*
markers =
    integration: marks tests that require database (deselect with '-m "not integration"')
```

**Key Settings**:
- `asyncio_mode = auto`: Automatically detect async tests
- `asyncio_default_fixture_loop_scope = function`: Each test gets own event loop

### Fixture Scopes

**Critical for async tests**:

```python
# ✅ CORRECT - Matching scopes
@pytest.fixture(scope="function")
async def event_loop():
    ...

@pytest.fixture(scope="function")
async def db_session(event_loop):
    ...

# ❌ WRONG - Mismatched scopes cause errors
@pytest.fixture(scope="module")  # Module scope
async def setup_database(event_loop):  # But depends on function-scoped event_loop
    ...
```

**Rule**: Async fixtures should typically use `scope="function"` to avoid event loop conflicts.

## Common Test Patterns

### Unit Test Pattern

```python
import pytest
from app.core.game_engine import GameEngine
from app.models.game_models import GameState

class TestGameEngine:
    """Unit tests for game engine - no database required"""

    def test_something(self):
        """Test description"""
        # Arrange
        engine = GameEngine()
        state = GameState(game_id=uuid4(), league_id="sba", ...)

        # Act
        result = engine.some_method(state)

        # Assert
        assert result.success is True
```

### Integration Test Pattern

```python
import pytest
from app.database.operations import DatabaseOperations
from app.database.session import AsyncSessionLocal

@pytest.mark.integration
class TestDatabaseOperations:
    """Integration tests - requires database"""

    @pytest.fixture
    async def db_ops(self):
        """Create DatabaseOperations instance"""
        ops = DatabaseOperations()
        yield ops

    async def test_create_game(self, db_ops):
        """Test description"""
        # Arrange
        game_id = uuid4()

        # Act
        await db_ops.create_game(game_id=game_id, ...)

        # Assert
        game = await db_ops.get_game(game_id)
        assert game is not None
```

### Async Test Pattern

```python
import pytest

# pytest-asyncio automatically detects async tests
async def test_async_operation():
    result = await some_async_function()
    assert result is not None

# Or explicit marker (not required with asyncio_mode=auto)
@pytest.mark.asyncio
async def test_another_async_operation():
    ...
```

## Database Testing

### Test Database Setup

**Required Environment Variables** (`.env`):
```bash
DATABASE_URL=postgresql+asyncpg://paperdynasty:PASSWORD@10.10.0.42:5432/paperdynasty_dev
```

**Database Connection**:
- Integration tests use the **same database** as development
- Tests should clean up after themselves (fixtures handle this)
- Each test should create unique game IDs to avoid conflicts

### Transaction Rollback Pattern

```python
@pytest.fixture
async def db_session():
    """Provide isolated database session with automatic rollback"""
    async with AsyncSessionLocal() as session:
        async with session.begin():
            yield session
            # Automatic rollback on fixture teardown
```

**Note**: Current fixtures may not properly isolate transactions, contributing to connection conflicts.

## Known Test Issues

### 1. Player Model Test Failures

**Issue**: `tests/unit/models/test_player_models.py` has 13 failures

**Root Causes**:
- `BasePlayer.get_image_url()` not marked as `@abstractmethod`
- Factory methods (`from_api_response()`) expect `pos_1` field but test fixtures don't provide it
- Attribute name mismatch: tests expect `player_id` but model has `id`
- Display name format mismatch in `PdPlayer.get_display_name()`

**Files to Fix**:
- `app/models/player_models.py` - Update abstract methods and factory methods
- `tests/unit/models/test_player_models.py` - Update test fixtures to match API response format

### 2. Dice System Test Failure

**Issue**: `tests/unit/core/test_dice.py::TestRollHistory::test_get_rolls_since`

**Symptom**: Expects 1 roll but gets 0

**Likely Cause**: Roll history not properly persisting or timestamp filtering issue

### 3. Integration Test Connection Conflicts

**Issue**: 49 integration test errors due to AsyncPG connection conflicts

**Status**: **Known infrastructure issue** - not code bugs

**When It Matters**: Only when running multiple integration tests in sequence

**When It Doesn't**: Unit tests (474 passing) validate business logic

### 4. Event Loop Scope Mismatch

**Issue**: `tests/integration/test_state_persistence.py` - all 7 tests fail with scope mismatch

**Error**: `ScopeMismatch: You tried to access the function scoped fixture event_loop with a module scoped request object`

**Root Cause**: `setup_database` fixture is `scope="module"` but depends on `event_loop` which is `scope="function"`

**Fix**: Change `setup_database` to `scope="function"` or create module-scoped event loop

## Test Coverage

**Current Status** (as of 2025-11-01):
- ✅ **519 unit tests passing** (92% of unit tests)
  - Added 45 new tests for Phase 3B (X-Check tables and placeholders)
- ❌ **14 unit tests failing** (player models + 1 dice test - pre-existing)
- ❌ **49 integration test errors** (connection conflicts - infrastructure issue)
- ❌ **28 integration test failures** (various - pre-existing)

**Coverage by Module**:
```
app/config/                 ✅ 94/94 tests passing (+36 X-Check table tests)
  - test_league_configs.py      28 tests
  - test_play_outcome.py         30 tests
  - test_x_check_tables.py       36 tests (NEW - Phase 3B)
app/core/game_engine.py     ✅ Well covered (unit tests)
app/core/runner_advancement.py ✅ 60/60 tests passing (+9 X-Check placeholders)
  - test_runner_advancement.py   51 tests (groundball + placeholders)
  - test_flyball_advancement.py  21 tests
app/core/state_manager.py   ✅ 26/26 tests passing
app/core/dice.py            ⚠️  1 failure (roll history - pre-existing)
app/models/game_models.py   ✅ 60/60 tests passing
app/models/player_models.py ❌ 13/32 tests failing (pre-existing)
app/database/operations.py  ⚠️  Integration tests have infrastructure issues
```

## Testing Best Practices

### DO

- ✅ Write unit tests first (fast, reliable, no DB)
- ✅ Use descriptive test names: `test_game_ends_after_27_outs`
- ✅ Follow Arrange-Act-Assert pattern
- ✅ Use fixtures for common setup
- ✅ Test edge cases and error conditions
- ✅ Mock external dependencies (API calls, time, random)
- ✅ Keep tests independent (no shared state)
- ✅ Run unit tests frequently during development

### DON'T

- ❌ Don't run all integration tests at once (connection conflicts)
- ❌ Don't share state between tests
- ❌ Don't test implementation details (test behavior)
- ❌ Don't use real API calls in tests (use mocks)
- ❌ Don't depend on test execution order
- ❌ Don't skip writing tests because integration tests are flaky

### Mocking Examples

```python
from unittest.mock import Mock, patch, AsyncMock

# Mock database operations
@patch('app.core.game_engine.DatabaseOperations')
def test_with_mock_db(mock_db_class):
    mock_db = Mock()
    mock_db_class.return_value = mock_db
    mock_db.create_game = AsyncMock(return_value=None)

    # Test code that uses DatabaseOperations
    ...

# Mock dice rolls for deterministic tests
@patch('app.core.dice.DiceSystem.roll_d20')
def test_with_fixed_roll(mock_roll):
    mock_roll.return_value = 15
    # Test code expecting roll of 15
    ...

# Mock Pendulum time
with time_machine.travel("2025-10-31 12:00:00", tick=False):
    # Test time-dependent code
    ...
```

## Debugging Failed Tests

### Verbose Output

```bash
# Show full output including print statements
pytest tests/unit/core/test_game_engine.py -v -s

# Show local variables on failure
pytest tests/unit/core/test_game_engine.py -v -l

# Stop on first failure
pytest tests/unit/core/test_game_engine.py -v -x

# Show full traceback
pytest tests/unit/core/test_game_engine.py -v --tb=long
```

### Interactive Debugging

```bash
# Drop into debugger on failure
pytest tests/unit/core/test_game_engine.py --pdb

# Drop into debugger on first failure
pytest tests/unit/core/test_game_engine.py --pdb -x
```

### Logging in Tests

Tests capture logs by default. View with `-o log_cli=true`:

```bash
pytest tests/unit/core/test_game_engine.py -v -o log_cli=true -o log_cli_level=DEBUG
```

## CI/CD Considerations

**Recommended CI Test Strategy**:

```yaml
# Run fast unit tests on every commit
- name: Unit Tests
  run: pytest tests/unit/ -v --cov=app

# Run integration tests serially (slower but reliable)
- name: Integration Tests
  run: |
    pytest tests/integration/database/test_operations.py::TestDatabaseOperationsGame -v
    pytest tests/integration/database/test_operations.py::TestDatabaseOperationsLineup -v
    # ... run each test class separately
```

**OR** fix the integration test infrastructure first, then run normally.

## Troubleshooting

### "cannot perform operation: another operation is in progress"

**Solution**: Run integration tests individually or fix fixture scopes

### "Task got Future attached to a different loop"

**Solution**: Ensure all fixtures use `scope="function"` or create proper module-scoped event loop

### "No module named 'app'"

**Solution**:
```bash
# Set PYTHONPATH
export PYTHONPATH=/mnt/NV2/Development/strat-gameplay-webapp/backend

# Or run from backend directory
cd /mnt/NV2/Development/strat-gameplay-webapp/backend
pytest tests/unit/ -v
```

### Tests hang indefinitely

**Likely Cause**: Async test without proper event loop cleanup

**Solution**: Check fixture scopes and ensure `asyncio_mode = auto` in pytest.ini

### Database connection errors

**Check**:
1. PostgreSQL is running: `psql $DATABASE_URL`
2. `.env` has correct `DATABASE_URL`
3. Database exists and schema is migrated: `alembic upgrade head`

## Integration Test Refactor TODO

When refactoring integration tests to fix connection conflicts:

1. **Update fixtures in `tests/integration/conftest.py`**:
   - Change all fixtures to `scope="function"`
   - Ensure each test gets fresh database session
   - Implement proper session cleanup

2. **Add connection pooling**:
   - Consider using separate connection pool for tests
   - Or create new engine per test (slower but isolated)

3. **Add transaction rollback**:
   - Wrap each test in transaction
   - Rollback after test completes
   - Ensures database is clean for next test

4. **Consider pytest-xdist**:
   - Run tests in parallel with proper worker isolation
   - Each worker gets own database connection
   - Faster test execution

5. **Update `test_state_persistence.py`**:
   - Fix `setup_database` fixture scope mismatch
   - Consider splitting into smaller fixtures

## Additional Resources

- **pytest-asyncio docs**: https://pytest-asyncio.readthedocs.io/
- **AsyncPG docs**: https://magicstack.github.io/asyncpg/
- **SQLAlchemy async**: https://docs.sqlalchemy.org/en/20/orm/extensions/asyncio.html
- **Backend CLAUDE.md**: `../CLAUDE.md` - Main backend documentation

---

**Summary**: Unit tests are solid (91% passing), integration tests have known infrastructure issues that need fixture refactoring. Focus on unit tests for development, fix integration test infrastructure as separate task.