Speed up tests.

tests/conftest.py

@@ -1,21 +1,123 @@
 # ABOUTME: Pytest configuration and fixtures for AnimalTrack tests.
-# ABOUTME: Provides database fixtures, test clients, and common utilities.
+# ABOUTME: Provides database fixtures using template pattern for fast test isolation.
 
 import os
+import shutil
+import sqlite3
 import tempfile
+from pathlib import Path
 
 import pytest
+from filelock import FileLock
 
 from animaltrack.db import get_db
 from animaltrack.migrations import run_migrations
 
 
+def _get_template_dir() -> Path:
+    """Get shared template directory for all workers.
+
+    Uses system temp directory with a stable name so all pytest-xdist
+    workers find the same templates.
+    """
+    return Path(tempfile.gettempdir()) / "animaltrack_test_templates"
+
+
+def _checkpoint_wal(db_path: str) -> None:
+    """Checkpoint WAL file into main database for clean copy.
+
+    SQLite's WAL mode keeps changes in a separate -wal file. Before copying,
+    we checkpoint to merge all changes into the main .db file, then switch
+    to DELETE mode temporarily for a clean single-file state.
+    """
+    conn = sqlite3.connect(db_path)
+    try:
+        conn.execute("PRAGMA wal_checkpoint(TRUNCATE)")
+        conn.execute("PRAGMA journal_mode=DELETE")
+    finally:
+        conn.close()
+
+
+def _copy_db(src_path: Path, dest_path: Path) -> None:
+    """Copy SQLite database file.
+
+    Assumes source has been checkpointed and is in DELETE journal mode.
+    """
+    shutil.copy2(src_path, dest_path)
+
+
+@pytest.fixture(scope="session")
+def template_migrated_db(tmp_path_factory):
+    """Session-scoped template database with migrations applied.
+
+    Creates the template once across all xdist workers using file locking.
+    Returns the path to the template database (not a connection).
+    """
+    template_dir = _get_template_dir()
+    template_dir.mkdir(exist_ok=True)
+
+    template_path = template_dir / "migrated_template.db"
+    lock_path = template_dir / "migrated_template.lock"
+    marker_path = template_dir / "migrated_template.ready"
+
+    with FileLock(str(lock_path)):
+        if not marker_path.exists():
+            # First worker creates the template
+            run_migrations(str(template_path), "migrations", verbose=False)
+            _checkpoint_wal(str(template_path))
+            marker_path.touch()
+
+    return template_path
+
+
+@pytest.fixture(scope="session")
+def template_seeded_db(template_migrated_db, tmp_path_factory):
+    """Session-scoped template database with migrations and seeds.
+
+    Creates the seeded template once across all xdist workers.
+    Returns the path to the template database (not a connection).
+    """
+    from animaltrack.seeds import run_seeds
+
+    template_dir = _get_template_dir()
+    template_path = template_dir / "seeded_template.db"
+    lock_path = template_dir / "seeded_template.lock"
+    marker_path = template_dir / "seeded_template.ready"
+
+    with FileLock(str(lock_path)):
+        if not marker_path.exists():
+            # Copy from migrated template, then seed
+            _copy_db(template_migrated_db, template_path)
+            db = get_db(str(template_path))
+            run_seeds(db)
+            # Close connection and checkpoint
+            del db
+            _checkpoint_wal(str(template_path))
+            marker_path.touch()
+
+    return template_path
+
+
 @pytest.fixture
-def migrated_db(tmp_path):
-    """Create a database with migrations applied."""
-    db_path = str(tmp_path / "test.db")
-    run_migrations(db_path, "migrations", verbose=False)
-    return get_db(db_path)
+def migrated_db(template_migrated_db, tmp_path):
+    """Function-scoped database with migrations (isolated copy).
+
+    Creates a fast copy of the template for test isolation.
+    """
+    db_path = tmp_path / "test.db"
+    _copy_db(template_migrated_db, db_path)
+    return get_db(str(db_path))
+
+
+@pytest.fixture
+def seeded_db(template_seeded_db, tmp_path):
+    """Function-scoped database with migrations and seeds (isolated copy).
+
+    Creates a fast copy of the seeded template for test isolation.
+    """
+    db_path = tmp_path / "test.db"
+    _copy_db(template_seeded_db, db_path)
+    return get_db(str(db_path))
 
 
 @pytest.fixture
@@ -26,15 +128,6 @@ def temp_migrations_dir(tmp_path):
     return migrations_path
 
 
-@pytest.fixture
-def seeded_db(migrated_db):
-    """Database with migrations and seed data applied."""
-    from animaltrack.seeds import run_seeds
-
-    run_seeds(migrated_db)
-    return migrated_db
-
-
 @pytest.fixture
 def fresh_db_path(tmp_path):
     """Provide a path for a non-existent database file.
@@ -68,3 +161,15 @@ def temp_db_path():
         wal_path = db_path + suffix
         if os.path.exists(wal_path):
             os.unlink(wal_path)
+
+
+def pytest_sessionfinish(session, exitstatus):
+    """Clean up template databases after test session.
+
+    Only the master worker (or single-process mode) should clean up.
+    """
+    worker_id = os.environ.get("PYTEST_XDIST_WORKER", "master")
+    if worker_id == "master":
+        template_dir = _get_template_dir()
+        if template_dir.exists():
+            shutil.rmtree(template_dir, ignore_errors=True)