Initialise the Auth(entic|oris)ation packages

Initialise the authentication/authorisation system packages and set up the
initial database migrations to set up the system.

* README.md: Add documentation on migrations
* gn3/auth/__init__.py: init package
* gn3/auth/authentication/__init__.py: init package
* gn3/auth/authorisation/__init__.py: init package
* gn3/migrations.py: provide migration utilities
* migrations/auth/20221103_01_js9ub-initialise-the-auth-entic-oris-ation-database.py:
  new migration
* tests/unit/auth/test_init_database.py: test new migration applies and rolls
  back as expected
* tests/unit/conftest.py: fixtures for unit tests
* yoyo.auth.ini: basic configuration for yoyo-migration for auth system
  migrations

2 files changed, 73 insertions, 0 deletions

diff --git a/tests/unit/auth/test_init_database.py b/tests/unit/auth/test_init_database.py
new file mode 100644
index 0000000..bf1ed1d
--- /dev/null
+++ b/tests/unit/auth/test_init_database.py
@@ -0,0 +1,29 @@
+"""Test the auth database initialisation migration."""
+from contextlib import closing
+
+import pytest
+import sqlite3
+
+from gn3.migrations import get_migration, apply_migrations, rollback_migrations
+from tests.unit.conftest import (
+    apply_single_migration, rollback_single_migration)
+
+migration_path = "migrations/auth/20221103_01_js9ub-initialise-the-auth-entic-oris-ation-database.py"
+
+@pytest.mark.unit_test
+def test_initialise_the_database(auth_testdb):
+    with closing(sqlite3.connect(auth_testdb)) as conn, closing(conn.cursor()) as cursor:
+        cursor.execute("SELECT name FROM sqlite_schema WHERE type='table'")
+        result = cursor.fetchall()
+        assert "users" not in [row[0] for row in cursor.fetchall()]
+        apply_single_migration(auth_testdb, get_migration(migration_path))
+        cursor.execute("SELECT name FROM sqlite_schema WHERE type='table'")
+        assert "users" in [row[0] for row in cursor.fetchall()]
+
+@pytest.mark.unit_test
+def test_rollback_initialise_the_database(auth_testdb):
+    with closing(sqlite3.connect(auth_testdb)) as conn, closing(conn.cursor()) as cursor:
+        apply_single_migration(auth_testdb, get_migration(migration_path))
+        rollback_single_migration(auth_testdb, get_migration(migration_path))
+        cursor.execute("SELECT name FROM sqlite_schema WHERE type='table'")
+        assert "users" not in [row[0] for row in cursor.fetchall()]
diff --git a/tests/unit/conftest.py b/tests/unit/conftest.py
new file mode 100644
index 0000000..bc974d9
--- /dev/null
+++ b/tests/unit/conftest.py
@@ -0,0 +1,44 @@
+"""Fixtures for unit tests."""
+from typing import Union
+from pathlib import Path
+from datetime import datetime
+from tempfile import TemporaryDirectory
+
+import pytest
+from yoyo import get_backend
+from yoyo.migrations import Migration, MigrationList
+
+from gn3.app import create_app
+from gn3.migrations import apply_migrations, rollback_migrations
+
+@pytest.fixture(scope="session")
+def client():
+    """Create a test client fixture for tests"""
+    # Do some setup
+    with TemporaryDirectory() as testdir:
+        testdb = Path(testdir).joinpath(
+            f'testdb_{datetime.now().strftime("%Y%m%dT%H%M%S")}')
+        app = create_app({"AUTH_DB": testdb})
+        app.config.update({"TESTING": True})
+        app.testing = True
+        yield app.test_client()
+        # Clean up after ourselves
+        testdb.unlink(missing_ok=True)
+
+@pytest.fixture()
+def test_app_config(client): # pylint: disable=redefined-outer-name
+    """Return the test application's configuration object"""
+    return client.application.config
+
+@pytest.fixture()
+def auth_testdb(test_app_config): # pylint: disable=redefined-outer-name
+    """Get the test application's auth database file"""
+    return test_app_config["AUTH_DB"]
+
+def apply_single_migration(db_uri: Union[Path, str], migration: Migration):
+    """Utility to apply a single migration"""
+    apply_migrations(get_backend(f"sqlite:///{db_uri}"), MigrationList([migration]))
+
+def rollback_single_migration(db_uri: Union[Path, str], migration: Migration):
+    """Utility to rollback a single migration"""
+    rollback_migrations(get_backend(f"sqlite:///{db_uri}"), MigrationList([migration]))