1. Mike Bayer
  2. sqlalchemy


sqlalchemy / README.unittests.rst


NOTE: SQLAlchemy as of 0.9.4 now standardizes on pytest for test running! However, the existing support for Nose still remains! That is, you can now run the tests via pytest or nose. We hope to keep the suite nose-compatible indefinitely however this might change at some point.

SQLAlchemy unit tests by default run using Python's built-in sqlite3 module. If running on a Python installation that doesn't include this module, then pysqlite or compatible must be installed.

Unit tests can be run with pytest or nose:

py.test: http://pytest.org/

nose: https://pypi.python.org/pypi/nose/

The suite includes enhanced support when running with pytest.

SQLAlchemy implements plugins for both pytest and nose that must be present when tests are run. In the case of pytest, this plugin is automatically used when pytest is run against the SQLAlchemy source tree. However, for Nose support, a special test runner script must be used.

The test suite as also requires the mock library. While mock is part of the Python standard library as of 3.3, previous versions will need to have it installed, and is available at:



A plain vanilla run of all tests using sqlite can be run via setup.py, and requires that pytest is installed:

$ python setup.py test


To run all tests:

$ py.test

The pytest configuration in setup.cfg will point the runner at the test/ directory, where it consumes a conftest.py file that gets everything else up and running.


When using Nose, a bootstrap script is provided which sets up sys.path as well as installs the nose plugin:

$ ./sqla_nose.py

Assuming all tests pass, this is a very unexciting output. To make it more interesting:

$ ./sqla_nose.py -v


Any directory of test modules can be run at once by specifying the directory path, and a specific file can be specified as well:

$ py.test test/dialect

$ py.test test/orm/test_mapper.py

When using nose, the setup.cfg currently sets "where" to "test/", so the "test/" prefix is omitted:

$ ./sqla_nose.py dialect/

$ ./sqla_nose.py orm/test_mapper.py

With Nose, it is often more intuitive to specify tests as module paths:

$ ./sqla_nose.py test.orm.test_mapper

Nose can also specify a test class and optional method using this syntax:

$ ./sqla_nose.py test.orm.test_mapper:MapperTest.test_utils

With pytest, the -k flag is used to limit tests:

$ py.test test/orm/test_mapper.py -k "MapperTest and test_utils"


SQLAlchemy-specific options are added to both runners, which are viewable within the help screen. With pytest, these options are easier to locate as they are underneath the "sqlalchemy" grouping:

$ py.test --help

$ ./sqla_nose.py --help

The --help screen is a combination of common nose options and options which the SQLAlchemy nose plugin adds. The most commonly SQLAlchemy-specific options used are '--db' and '--dburi'.

Both pytest and nose support the same set of SQLAlchemy options, though pytest features a bit more capability with them.


Tests will target an in-memory SQLite database by default. To test against another database, use the --dburi option with any standard SQLAlchemy URL:


If you'll be running the tests frequently, database aliases can save a lot of typing. The --dbs option lists the built-in aliases and their matching URLs:

$ py.test --dbs
Available --db options (use --dburi to override)
           mysql    mysql://scott:tiger@
          oracle    oracle://scott:tiger@
        postgresql    postgresql://scott:tiger@

To run tests against an aliased database:

$ py.test --db postgresql

This list of database urls is present in the setup.cfg file. The list can be modified/extended by adding a file test.cfg at the top level of the SQLAlchemy source distribution which includes additional entries:


Your custom entries will override the defaults and you'll see them reflected in the output of --dbs.


As of SQLAlchemy 0.9.4, the test runner supports multiple databases at once. This doesn't mean that the entire test suite runs for each database, but instead specific test suites may do so, while other tests may choose to run on a specific target out of those available. For example, if the tests underneath test/dialect/ are run, the majority of these tests are either specific to a particular backend, or are marked as "multiple", meaning they will run repeatedly for each database in use. If one runs the test suite as follows:

$ py.test test/dialect --db sqlite --db postgresql --db mysql

The tests underneath test/dialect/test_suite.py will be tripled up, running as appropriate for each target database, whereas dialect-specific tests within test/dialect/mysql, test/dialect/postgresql/ test/dialect/test_sqlite.py should run fully with no skips, as each suite has its target database available.

The multiple targets feature is available both under pytest and nose, however when running nose, the "multiple runner" feature won't be available; instead, the first database target will be used.

When running with multiple targets, tests that don't prefer a specific target will be run against the first target specified. Putting sqlite first in the list will lead to a much faster suite as the in-memory database is extremely fast for setting up and tearing down tables.


Use an empty database and a database user with general DBA privileges. The test suite will be creating and dropping many tables and other DDL, and preexisting tables will interfere with the tests.

Several tests require alternate usernames or schemas to be present, which are used to test dotted-name access scenarios. On some databases such as Oracle or Sybase, these are usernames, and others such as Postgresql and MySQL they are schemas. The requirement applies to all backends except SQLite and Firebird. The names are:

test_schema_2 (only used on Postgresql)

Please refer to your vendor documentation for the proper syntax to create these namespaces - the database user must have permission to create and drop tables within these schemas. Its perfectly fine to run the test suite without these namespaces present, it only means that a handful of tests which expect them to be present will fail.

Additional steps specific to individual databases are as follows:

POSTGRESQL: To enable unicode testing with JSONB, create the
database with UTF8 encoding::

    postgres=# create database test with owner=scott encoding='utf8' template=template0;

To include tests for HSTORE, create the HSTORE type engine::

    postgres=# \c test;
    You are now connected to database "test" as user "postgresql".
    test=# create extension hstore;

MYSQL: Default storage engine should be "MyISAM".   Tests that require
"InnoDB" as the engine will specify this explicitly.

ORACLE: a user named "test_schema" is created.

The primary database user needs to be able to create and drop tables,
synonyms, and constraints within the "test_schema" user.   For this
to work fully, including that the user has the "REFERENCES" role
in a remote schema for tables not yet defined (REFERENCES is per-table),
it is required that the test the user be present in the "DBA" role:

    grant dba to scott;

SYBASE: Similar to Oracle, "test_schema" is created as a user, and the
primary test user needs to have the "sa_role".

It's also recommended to turn on "trunc log on chkpt" and to use a
separate transaction log device - Sybase basically seizes up when
the transaction log is full otherwise.

A full series of setup assuming sa/master:

    disk init name="translog", physname="/opt/sybase/data/translog.dat", size="10M"
    create database sqlalchemy on default log on translog="10M"
    sp_dboption sqlalchemy, "trunc log on chkpt", true
    sp_addlogin scott, "tiger7"
    sp_addlogin test_schema, "tiger7"
    use sqlalchemy
    sp_adduser scott
    sp_adduser test_schema
    grant all to scott
    sp_role "grant", sa_role, scott

Sybase will still freeze for up to a minute when the log becomes
full.  To manually dump the log::

    dump tran sqlalchemy with truncate_only

MSSQL: Tests that involve multiple connections require Snapshot Isolation
ability implemented on the test database in order to prevent deadlocks that
will occur with record locking isolation. This feature is only available
with MSSQL 2005 and greater. You must enable snapshot isolation at the
database level and set the default cursor isolation with two SQL commands:



MSSQL+zxJDBC: Trying to run the unit tests on Windows against SQL Server
requires using a test.cfg configuration file as the cmd.exe shell won't
properly pass the URL arguments into the nose test runner.

POSTGRESQL: Full-text search configuration should be set to English, else
several tests of ``.match()`` will fail. This can be set (if it isn't so
already) with:

 ALTER DATABASE test SET default_text_search_config = 'pg_catalog.english'


SQLAlchemy logs its activity and debugging through Python's logging package. Any log target can be directed to the console with command line options, such as:

$ ./sqla_nose.py test.orm.unitofwork --log-info=sqlalchemy.orm.mapper \
  --log-debug=sqlalchemy.pool --log-info=sqlalchemy.engine

This would log mapper configuration, connection pool checkouts, and SQL statement execution.


Coverage is tracked using the coverage plugins built for pytest or nose:

$ py.test test/sql/test_query --cov=sqlalchemy

$ ./sqla_nose.py test.sql.test_query --with-coverage

BIG COVERAGE TIP !!! There is an issue where existing .pyc files may store the incorrect filepaths, which will break the coverage system. If coverage numbers are coming out as low/zero, try deleting all .pyc files.


See the file README.dialects.rst for detail on dialects.


If you want to test across multiple versions of Python, you may find tox useful. SQLAlchemy includes a tox.ini file:

tox -e full

SQLAlchemy uses tox mostly for pre-fab testing configurations, to simplify configuration of Jenkins jobs, and not for testing different Python interpreters simultaneously. You can of course create whatever alternate tox.ini file you want.

Environments include:

"full" - runs a full py.test

"coverage" - runs a py.test plus coverage, skipping memory/timing
intensive tests

"pep8" - runs flake8 against the codebase (useful with --diff to check
against a patch)


Parallel testing is supported using the Pytest xdist plugin. Supported databases currently include sqlite, postgresql, and mysql. The username for the database should have CREATE DATABASE and DROP DATABASE privileges. After installing pytest-xdist, testing is run adding the -n<num> option. For example, to run against sqlite, mysql, postgresql with four processes:

tox -e -- -n 4 --db sqlite --db postgresql --db mysql

Each backend has a different scheme for setting up the database. Postgresql still needs the "test_schema" and "test_schema_2" schemas present, as the parallel databases are created using the base database as a "template".