# 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)
```

## Testing Policy

**🚨 REQUIRED: 100% unit tests passing before committing to any feature branch.**

### Commit Policy

This project enforces a strict testing policy to maintain code quality and prevent regressions.

**Before Every Commit:**
- ✅ **MUST**: Run `uv run pytest tests/unit/ -q`
- ✅ **MUST**: All 609 unit tests passing (100%)
- ✅ **MUST**: Fix any failing tests before committing
- ⚠️ **OPTIONAL**: Use `--no-verify` for `[WIP]` commits (feature branches only)

**Before Merging to Main:**
- ✅ **MUST**: 100% unit tests passing
- ✅ **MUST**: Code review approval
- ✅ **MUST**: CI/CD green build
- ❌ **NEVER**: Merge with failing tests

**Automated Enforcement:**

A git pre-commit hook is available to automatically run tests before each commit.

```bash
# Install the hook (one-time setup)
cd /mnt/NV2/Development/strat-gameplay-webapp/backend
cp .git-hooks/pre-commit .git/hooks/pre-commit
chmod +x .git/hooks/pre-commit
```

See `backend/CLAUDE.md` → "Testing Policy" section for full details.

### Current Test Baseline

**Must maintain or improve:**
- ✅ Unit tests: **979/979 passing (100%)**
- ✅ Integration tests: **32/32 passing (100%)**
- ⏱️ Unit execution: **~4 seconds**
- ⏱️ Integration execution: **~5 seconds**
- 📊 Coverage: High coverage of core systems

## Running Tests

### Unit Tests (Recommended)

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

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

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

# With coverage
uv run 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)

**✅ Integration tests now work reliably** using session injection pattern.

```bash
# Run all integration tests
uv run pytest tests/integration/database/test_operations.py -v

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

# Run with markers
uv run pytest tests/ -v -m integration
```

#### Session Injection Pattern (IMPORTANT)

Integration tests use **session injection** to avoid asyncpg connection conflicts:

```python
# tests/integration/conftest.py
@pytest_asyncio.fixture(scope="function")
async def db_session():
    """Provide isolated database session with automatic rollback"""
    async with TestAsyncSessionLocal() as session:
        yield session
        await session.rollback()  # Cleanup after test

@pytest_asyncio.fixture(scope="function")
async def db_ops(db_session: AsyncSession):
    """DatabaseOperations with injected session"""
    return DatabaseOperations(db_session)  # All operations share this session
```

**Key Points**:
- Each test gets its own session (no connection conflicts)
- Session is rolled back after test (automatic cleanup)
- Tests use `NullPool` to prevent connection reuse issues
- All `db_ops` methods use the same session (no "operation in progress" errors)

See `app/database/CLAUDE.md` for full session injection documentation.

### All Tests

```bash
# Run everything
uv run pytest tests/ -v

# Run with markers
uv run pytest tests/ -v -m "not integration"  # Skip integration tests
uv run 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 (Session Injection)

```python
import pytest
from uuid import uuid4

# Mark all tests in module as integration tests
pytestmark = pytest.mark.integration

class TestDatabaseOperations:
    """Integration tests - use fixtures from tests/integration/conftest.py"""

    async def test_create_game(self, db_ops, db_session):
        """
        Test creating a game in database.

        Uses db_ops fixture (DatabaseOperations with injected session)
        and db_session for flush/visibility within transaction.
        """
        # Arrange
        game_id = uuid4()

        # Act
        game = await db_ops.create_game(
            game_id=game_id,
            league_id="sba",
            home_team_id=1,
            away_team_id=2,
            game_mode="friendly",
            visibility="public"
        )
        await db_session.flush()  # Make visible within session

        # Assert
        retrieved = await db_ops.get_game(game_id)
        assert retrieved is not None
        assert retrieved.id == game_id
        # Session automatically rolled back after test
```

**Key Pattern Notes**:
- Fixtures (`db_ops`, `db_session`) come from `tests/integration/conftest.py`
- Use `await db_session.flush()` to persist changes within test (not `commit()`)
- Session is automatically rolled back after each test (isolation)
- All operations share same session (no connection conflicts)

### 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 (tests/integration/conftest.py)

```python
from sqlalchemy import NullPool
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker

# Use NullPool to prevent connection reuse issues in tests
test_engine = create_async_engine(DATABASE_URL, poolclass=NullPool)
TestAsyncSessionLocal = async_sessionmaker(test_engine, class_=AsyncSession, expire_on_commit=False)

@pytest_asyncio.fixture(scope="function")
async def db_session():
    """Provide isolated database session with automatic rollback"""
    async with TestAsyncSessionLocal() as session:
        yield session
        await session.rollback()  # Cleanup - discard all changes

@pytest_asyncio.fixture(scope="function")
async def db_ops(db_session: AsyncSession):
    """DatabaseOperations with injected session for test isolation"""
    return DatabaseOperations(db_session)
```

**Why This Works**:
- `NullPool`: Prevents asyncpg connection reuse issues
- `scope="function"`: Each test gets fresh session
- `rollback()`: Automatically discards all test data
- Session injection: All `db_ops` methods use same session (no conflicts)

## Known Test Issues

All major test infrastructure issues have been resolved. The test suite is now stable.

### Historical Context (Resolved)

**AsyncPG Connection Conflicts** - **RESOLVED** (2025-11-27)
- **Was**: "cannot perform operation: another operation is in progress" errors
- **Fix**: Session injection pattern in `DatabaseOperations` + `NullPool` in test fixtures
- **Result**: 32/32 integration tests now passing

## Test Coverage

**Current Status** (as of 2025-11-27):
- ✅ **979 unit tests passing** (100%)
- ✅ **32 integration tests passing** (100%)
- **Total: 1,011 tests passing**

**Coverage by Module**:
```
app/config/                 ✅ Well covered
app/core/game_engine.py     ✅ Well covered (unit + integration)
app/core/state_manager.py   ✅ Well covered
app/core/dice.py            ✅ Well covered
app/models/                 ✅ Well covered
app/database/operations.py  ✅ 32 integration tests (session injection pattern)
app/websocket/handlers.py   ✅ 148 WebSocket handler tests
app/middleware/             ✅ Rate limiting, exceptions tested
```

## 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 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 use `commit()` in integration tests (use `flush()` - session auto-rollbacks)
- ❌ Don't create `DatabaseOperations()` without session injection in integration tests

### 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
uv run pytest tests/unit/core/test_game_engine.py -v -s

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

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

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

### Interactive Debugging

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

# Drop into debugger on first failure
uv run 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
uv run 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: uv run pytest tests/unit/ -v --cov=app

# Run integration tests (session injection pattern makes these reliable)
- name: Integration Tests
  run: uv run pytest tests/integration/database/test_operations.py -v
```

**All tests can now run together** thanks to session injection pattern.

## Troubleshooting

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

**This issue is RESOLVED.** If you see it, you're likely:
- Creating `DatabaseOperations()` without session injection in tests
- Not using the `db_ops` fixture from `tests/integration/conftest.py`

**Solution**: Use session injection pattern:
```python
async def test_something(self, db_ops, db_session):  # Use fixtures!
    await db_ops.create_game(...)  # Uses injected session
```

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

**Solution**: Ensure all fixtures use `scope="function"` (already configured in conftest.py)

### "No module named 'app'"

**Solution**:
```bash
# Recommended: Use UV (handles PYTHONPATH automatically)
cd /mnt/NV2/Development/strat-gameplay-webapp/backend
uv run pytest tests/unit/ -v

# Alternative: Set PYTHONPATH manually
export PYTHONPATH=/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 Architecture (Completed 2025-11-27)

The integration test infrastructure has been fully refactored using session injection:

### Key Components

1. **`tests/integration/conftest.py`**:
   - `NullPool` engine (prevents connection reuse issues)
   - `db_session` fixture (function-scoped, auto-rollback)
   - `db_ops` fixture (`DatabaseOperations` with injected session)

2. **`app/database/operations.py`**:
   - Constructor accepts optional `AsyncSession`
   - `_get_session()` context manager handles both modes
   - Methods use `flush()` not `commit()`

3. **`app/core/game_engine.py`**:
   - Creates `DatabaseOperations(session)` for transaction groups
   - Ensures atomic save_play + update_game_state operations

### Pattern Summary

```
Production:  db_ops = DatabaseOperations()        → Auto-commit per operation
Testing:     db_ops = DatabaseOperations(session) → Shared session, caller controls
Transactions: db_ops = DatabaseOperations(session) → Multiple ops, single commit
```

## Additional Resources

- **Database CLAUDE.md**: `app/database/CLAUDE.md` - Full session injection documentation
- **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

---

**Summary**: All 1,011 tests passing (979 unit + 32 integration). Session injection pattern ensures reliable, isolated integration tests with automatic cleanup.
