fake-session-maker 0.0.2

Create a SQLAlchemy session_maker that won't commit to db for testing purposes.

fake_session_maker

The fake_session_maker is a SQLAlchemy and Pytest-based package designed to facilitate database testing by replacing a classic SQLAlchemy SessionMaker context manager.

Features

• Replaces the SQLAlchemy SessionMaker context manager with a "read-only" session during tests.
• Rollbacks database state at the end of each test, ensuring isolation between tests.
• Simple fixture-based usage integrates smoothly with your Pytest suite.

Drawbacks

Code that plan to be tested using fake_session_maker have the following limitations:

• Prevent the use of SessionMaker.rollback() by hands as every previous "prod-only" commit will be rolled back too
• Cannot rely on results after a forced SessionMaker.rollback() if a SessionMaker.flush() fails for the same reason as above

Mitigation

• For such tests, a snapshot of the database can be taken before the test and restored after the test using a fixture. This is not provided by fake_session_maker but can be implemented by the user. This is more expensive than using fake_session_maker but won't suffer from the drawbacks

Prerequisites

To use fake_session_maker, you'll need:

• Python (>=3.7)
• SQLAlchemy (>=1.4 <3.0)
• Pytest (>=6.2.2)

Usage

Define the fixture

Below is an example of how to use fake_session_maker in a pytest fixture:

import pytest
from fake_session_maker import fsm


# Assuming Namespace is where the session_maker is defined

@pytest.fixture
def fake_session_maker():
    with fsm(
            db_url="sqlite:///tests/test.sqlite",
            namespace=Namespace,
            symbol_name="session_maker",
    ) as fake_session_maker_:
        yield fake_session_maker_

# Now, you can use fake_session_maker in your tests

Use the fixture

Below is an example of how to use fake_session_maker fixture in a test:

# Each test will have a fresh database, empty of any data
@pytest.mark.parametrize("name", ["jane", "joe"])
def test_create_example(fake_session_maker, name):
    result = create_example('test')
    assert result == 'success'
    with fake_session_maker() as session:
        # Each time we check, only the data created in this test will be present
        assert session.query(models.User).count() == 1

See the tests.test_fsm.py directory for a full example.

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for more details.

Testing

If you want to run the tests locally, you can follow instructions here: CONTRIBUTING.md #testing.

License

Distributed under the MIT License. See LICENSE for more information.