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pytest-postgresql

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What is this?

This is a pytest plugin, that enables you to test your code that relies on a running PostgreSQL Database.
It allows you to specify fixtures for PostgreSQL process and client.

How to use

.. warning::

Tested on PostgreSQL versions >= 10. See tests for more details.

Install with:

.. code-block:: sh

pip install pytest-postgresql

You will also need to install psycopg. See its installation instructions <https://www.psycopg.org/psycopg3/docs/basic/install.html>.
Note that this plugin requires psycopg version 3. It is possible to simultaneously install version 3
and version 2 for libraries that require the latter (see those instructions <https://www.psycopg.org/docs/install.html>).

Plugin contains three fixtures:

postgresql - it's a client fixture that has functional scope.
After each test it ends all leftover connections, and drops test database
from PostgreSQL ensuring repeatability.
This fixture returns already connected psycopg connection.
postgresql_proc - session scoped fixture, that starts PostgreSQL instance
at it's first use and stops at the end of the tests.
postgresql_noproc - a noprocess fixture, that's connecting to already
running postgresql instance.
For example on dockerized test environments, or CI providing postgresql services

Simply include one of these fixtures into your tests fixture list.

You can also create additional postgresql client and process fixtures if you'd need to:

.. code-block:: python

from pytest_postgresql import factories

postgresql_my_proc = factories.postgresql_proc(
    port=None, unixsocketdir='/var/run')
postgresql_my = factories.postgresql('postgresql_my_proc')

.. note::

Each PostgreSQL process fixture can be configured in a different way than the others through the fixture factory arguments.

Sample test

.. code-block:: python

def test_example_postgres(postgresql):
    """Check main postgresql fixture."""
    cur = postgresql.cursor()
    cur.execute("CREATE TABLE test (id serial PRIMARY KEY, num integer, data varchar);")
    postgresql.commit()
    cur.close()

Pre-populating the database for tests

If you want the database fixture to be automatically pre-populated with your schema and data, there are two lewels you can achieve it:

#. per test in a client fixture, by an intermediary fixture between client and your test (or other fixtures)
#. per session in a process fixture

The process fixture accepts a load parameter, which accepts these loaders:

sql file path - which will load and execute sql files
loading functions - either by string import path, actual callable.
Loading functions will receive host, port, user, dbname and password arguments and will have to perform
connection to the database inside. Or start session in the ORM of your choice to perform actions with given ORM.
This way, you'd be able to trigger ORM based data manipulations, or even trigger database migrations programmatically.

The process fixture pre-populates the database once per test session (at the start of the process fixture),
and loads the schema and data into the template database. Client fixture then creates test database out of the template database each test,
which significantly speeds up the tests.

.. code-block:: python

from pathlib import Path
postgresql_my_proc = factories.postgresql_proc(
    load=[Path("schemafile.sql"), Path("otherschema.sql"), "import.path.to.function", "import.path.to:otherfunction", load_this]
)

Additional benefit, is that test code might safely use separate database connection, and can safely test it's behaviour with transactions and rollbacks,
as tests and code will work on separate database connections.

Defining pre-populate on command line:

.. code-block:: sh

pytest --postgresql-populate-template=path.to.loading_function --postgresql-populate-template=path.to.other:loading_function --postgresql-populate-template=path/to/file.sql

Connecting to already existing postgresql database

Some projects are using already running postgresql servers (ie on docker instances).
In order to connect to them, one would be using the postgresql_noproc fixture.

.. code-block:: python

postgresql_external = factories.postgresql('postgresql_noproc')

By default the postgresql_noproc fixture would connect to postgresql instance using 5432 port. Standard configuration options apply to it.

These are the configuration options that are working on all levels with the postgresql_noproc fixture:

Configuration

You can define your settings in three ways, it's fixture factory argument, command line option and pytest.ini configuration option.
You can pick which you prefer, but remember that these settings are handled in the following order:

* ``Fixture factory argument``
* ``Command line option``
* ``Configuration option in your pytest.ini file``

.. list-table:: Configuration options
:header-rows: 1

- PostgreSQL option
- Fixture factory argument
- Command line option
- pytest.ini option
- Noop process fixture
- Default
- Path to executable
- executable
- --postgresql-exec
- postgresql_exec
- /usr/lib/postgresql/13/bin/pg_ctl
- host
- host
- --postgresql-host
- postgresql_host
- yes
- 127.0.0.1
- port
- port
- --postgresql-port
- postgresql_port
- yes (5432)
- random
- Port search count
- --postgresql-port-search-count
- postgresql_port_search_count
- 5
- postgresql user
- user
- --postgresql-user
- postgresql_user
- yes
- postgres
- password
- password
- --postgresql-password
- postgresql_password
- yes
- Starting parameters (extra pg_ctl arguments)
- startparams
- --postgresql-startparams
- postgresql_startparams
- -w
- Postgres exe extra arguments (passed via pg_ctl's -o argument)
- postgres_options
- --postgresql-postgres-options
- postgresql_postgres_options
- Location for unixsockets
- unixsocket
- --postgresql-unixsocketdir
- postgresql_unixsocketdir
- $TMPDIR
- Database name which will be created by the fixtures
- dbname
- --postgresql-dbname
- postgresql_dbname
- yes, however with xdist an index is being added to name, resulting in test0, test1 for each worker.
- test
- Default Schema either in sql files or import path to function that will load it (list of values for each)
- load
- --postgresql-load
- postgresql_load
- yes
- PostgreSQL connection options
- options
- --postgresql-options
- postgresql_options
- yes

Drop test database on start.

.. warning::

Use carefully as it might lead to unexpected results within your test suite.

--postgresql-drop-test-database
false

Example usage:

pass it as an argument in your own fixture

.. code-block:: python

  postgresql_proc = factories.postgresql_proc(
      port=8888)

use --postgresql-port command line option when you run your tests

.. code-block:: sh
```
  py.test tests --postgresql-port=8888
```
specify your port as postgresql_port in your pytest.ini file.

To do so, put a line like the following under the [pytest] section of your pytest.ini:

.. code-block:: ini
```
  [pytest]
  postgresql_port = 8888
```

Examples

Populating database for tests

With SQLAlchemy
+++++++++++++++

This example shows how to populate database and create an SQLAlchemy's ORM connection:

Sample below is simplified session fixture from
pyramid_fullauth <https://github.com/fizyk/pyramid_fullauth/>_ tests:

.. code-block:: python

from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy.pool import NullPool
from zope.sqlalchemy import register


@pytest.fixture
def db_session(postgresql):
    """Session for SQLAlchemy."""
    from pyramid_fullauth.models import Base

    connection = f'postgresql+psycopg2://{postgresql.info.user}:@{postgresql.info.host}:{postgresql.info.port}/{postgresql.info.dbname}'

    engine = create_engine(connection, echo=False, poolclass=NullPool)
    pyramid_basemodel.Session = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
    pyramid_basemodel.bind_engine(
        engine, pyramid_basemodel.Session, should_create=True, should_drop=True)

    yield pyramid_basemodel.Session

    transaction.commit()
    Base.metadata.drop_all(engine)


@pytest.fixture
def user(db_session):
    """Test user fixture."""
    from pyramid_fullauth.models import User
    from tests.tools import DEFAULT_USER

    new_user = User(**DEFAULT_USER)
    db_session.add(new_user)
    transaction.commit()
    return new_user


def test_remove_last_admin(db_session, user):
    """
    Sample test checks internal login, but shows usage in tests with SQLAlchemy
    """
    user = db_session.merge(user)
    user.is_admin = True
    transaction.commit()
    user = db_session.merge(user)

    with pytest.raises(AttributeError):
        user.is_admin = False

.. note::

See the original code at `pyramid_fullauth's conftest file <https://github.com/fizyk/pyramid_fullauth/blob/2950e7f4a397b313aaf306d6d1a763ab7d8abf2b/tests/conftest.py#L35>`_.
Depending on your needs, that in between code can fire alembic migrations in case of sqlalchemy stack or any other code

Maintaining database state outside of the fixtures

It is possible and appears it's used in other libraries for tests,
to maintain database state with the use of the pytest-postgresql database
managing functionality:

For this import DatabaseJanitor and use its init and drop methods:

.. code-block:: python

import pytest
from pytest_postgresql.janitor import DatabaseJanitor

@pytest.fixture
def database(postgresql_proc):
    # variable definition

    janitor = DatabaseJanitor(
        user=postgresql_proc.user,
        host=postgresql_proc.host,
        proc=postgresql_proc.port,
        testdb="my_test_database",
        version=postgresql_proc.version,
        password="secret_password",
    )
    janitor.init()
    yield psycopg2.connect(
        dbname="my_test_database",
        user=postgresql_proc.user,
        password="secret_password",
        host=postgresql_proc.host,
        port=postgresql_proc.port,
    )
    janitor.drop()

or use it as a context manager:

.. code-block:: python

import pytest
from pytest_postgresql.janitor import DatabaseJanitor

@pytest.fixture
def database(postgresql_proc):
    # variable definition

    with DatabaseJanitor(
        user=postgresql_proc.user,
        host=postgresql_proc.host,
        port=postgresql_proc.port,
        dbname="my_test_database",
        version=postgresql_proc.version,
        password="secret_password",
    ):
        yield psycopg2.connect(
            dbname="my_test_database",
            user=postgresql_proc.user,
            password="secret_password",
            host=postgresql_proc.host,
            port=postgresql_proc.port,
        )

.. note::

DatabaseJanitor manages the state of the database, but you'll have to create
connection to use in test code yourself.

You can optionally pass in a recognized postgresql ISOLATION_LEVEL for
additional control.

.. note::

See DatabaseJanitor usage in python's warehouse test code https://github.com/pypa/warehouse/blob/5d15bfe/tests/conftest.py#L127

Connecting to Postgresql (in a docker)

To connect to a docker run postgresql and run test on it, use noproc fixtures.

.. code-block:: sh

docker run --name some-postgres -e POSTGRES_PASSWORD=mysecretpassword -d postgres

This will start postgresql in a docker container, however using a postgresql installed locally is not much different.

In tests, make sure that all your tests are using postgresql_noproc fixture like that:

.. code-block:: python

from pytest_postgresql import factories


postgresql_in_docker = factories.postgresql_noproc()
postgresql = factories.postgresql("postgresql_in_docker", dbname="test")


def test_postgres_docker(postgresql):
    """Run test."""
    cur = postgresql.cursor()
    cur.execute("CREATE TABLE test (id serial PRIMARY KEY, num integer, data varchar);")
    postgresql.commit()
    cur.close()

And run tests:

.. code-block:: sh

pytest --postgresql-host=172.17.0.2 --postgresql-password=mysecretpassword

Basic database state for all tests

If you've got several tests that require common initialisation, you can to define a load and pass it to
your custom postgresql process fixture:

.. code-block:: python

import pytest_postgresql.factories
def load_database(**kwargs):
    db_connection: connection = psycopg2.connect(**kwargs)
    with db_connection.cursor() as cur:
        cur.execute("CREATE TABLE stories (id serial PRIMARY KEY, name varchar);")
        cur.execute(
            "INSERT INTO stories (name) VALUES"
            "('Silmarillion'), ('Star Wars'), ('The Expanse'), ('Battlestar Galactica')"
        )
        db_connection.commit()

postgresql_proc = factories.postgresql_proc(
    load=[load_database],
)

postgresql = factories.postgresql(
    "postgresql_proc",
)

The way this will work is that the process fixture will populate template database,
which in turn will be used automatically by client fixture to create a test database from scratch.
Fast, clean and no dangling transactions, that could be accidentally rolled back.

Same approach will work with noproces fixture, while connecting to already running postgresql instance whether
it'll be on a docker machine or running remotely or locally.

Using SQLAlchemy to initialise basic database state
+++++++++++++++++++++++++++++++++++++++++++++++++++

How to use SQLAlchemy for common initialisation:

.. code-block:: python

def load_database(**kwargs):
    connection = f"postgresql+psycopg2://{kwargs['user']}:@{kwargs['host']}:{kwargs['port']}/{kwargs['dbname']}"
    engine = create_engine(connection)
    Base.metadata.create_all(engine)
    session = scoped_session(sessionmaker(bind=engine))
    # add things to session
    session.commit()

postgresql_proc = factories.postgresql_proc(load=[load_database])

postgresql = factories.postgresql('postgresql_proc') # still need to check if this is actually needed or not

@pytest.fixture
def dbsession(postgresql):
    connection = f'postgresql+psycopg2://{postgresql.info.user}:@{postgresql.info.host}:{postgresql.info.port}/{postgresql.info.dbname}'
    engine = create_engine(connection)

    session = scoped_session(sessionmaker(bind=engine))

    yield session
    # 'Base.metadata.drop_all(engine)' here specifically does not work. It is also not needed. If you leave out the session.close()
    # all the tests still run, but you get a warning/error at the end of the tests.
    session.close()

Release

Install pipenv and --dev dependencies first, Then run:

.. code-block:: sh

pipenv run tbump [NEW_VERSION]

Dependency	Optional
mirakuru	false
packaging	false
port-for	false
psycopg	false
pytest	false

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pytest-postgresql

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