pytest_sqlalchemy_fixtures.py

@pytest.fixture(autouse=True, scope='session')
def inject_test_settings(tmpdir_factory):
    # cleans environment vars, sets up some temp space and data, etc


@pytest.fixture(autouse=True, scope='session')
def test_db(inject_test_settings):
    # creates the test database [once] at the beginning of the test suite.
    # drops it at the end of the suite.


@pytest.fixture(autouse=True, scope='session')
def test_engine(test_db):
    # turn SAWarnings into exceptions when running tests
    warnings.simplefilter('error', SAWarning)
    if 'test' not in config.db_name:
        # Sanity check to ensure that the `inject_test_settings` fixture has applied correctly.
        pytest.fail(msg='The test settings have not been injected yet!')
    db_url = ... # point it at test db created by prev fixture
    engine = create_engine(db_url)
    Session.configure(bind=engine)
    Base.metadata.create_all(bind=engine)  # create tables at the beginning of test suite
    yield engine
    Base.metadata.drop_all(bind=engine)  # drop tables at the end of test suite


@pytest.fixture
def session(test_engine):
    connection = test_engine.connect()
    transaction = connection.begin()
    Session.configure(bind=connection)
    the_session = Session(bind=connection)
    yield the_session
    # you don't actually need to use this session if you wan't to, but it can be convenient.
    # new sessions created from Session() will also be bound to the test engine's connection.
    the_session.close()
    transaction.rollback()
    connection.close()