Package: van.pg
Test PostgreSQL DatabasesEasy creation of PostgreSQL databases (and clusters) for unit testing.Dirty DatabasesTest databases take a long time to create. In general you need to be a little
careful when you decide to delete/recreate a test database fixture.Also, there seems to be no robust way in PostgreSQL of figuring out if a
database was committed to or not.So van.pg has no choice but to place the responsibility on the you to notify
it when a database is dirty.  If this isn’t done properly, test isolation will
be compromised.  It’s not ideal, but the best we can do.One exception is if you consistently use thetransactionpackage
(http://pypi.python.org/pypi/transaction) to manage database commits.  In this
case you can ask for the resource to be dirtied whenever a transaction is
committed.Integration withtestresourcesThe typical way to use these fixtures is viatestresources(http://pypi.python.org/pypi/testresources/):>>> from testresources import ResourcedTestCase
>>> from van.pg import DatabaseManager
>>> import psycopg2>>> def init_db(db):
...     conn = psycopg2.connect(host=db.host, database=db.database)
...     cur = conn.cursor()
...     cur.execute("CREATE TABLE foo (bar INTEGER);")
...     conn.commit()
...     conn.close()>>> class MyTest(ResourcedTestCase):
...
...     resources = [('db', DatabaseManager(initialize_sql=init_db))]
...
...     def runTest(self):
...         conn = psycopg2.connect(host=self.db.host, database=self.db.database)
...         cur = conn.cursor()
...         cur.execute("INSERT INTO foo VALUES (1);")
...         conn.commit()
...         cur = conn.cursor()
...         cur.execute("SELECT * FROM foo")
...         self.assertEqual(cur.fetchall(), [(1, )])
...         # NOTE: must close connections or dropping databases fails
...         conn.close()
...         self.db.dirtied() # we changed the DB, so it needs re-loadingActually run the test:>>> from unittest import TextTestRunner
>>> import sys
>>> runner = TextTestRunner(stream=sys.stdout)
>>> runner.run(MyTest()) # doctest: +ELLIPSIS
.
...
OK
...Using template databasesIf you need to recreate the same database many times, it can be faster to let
PostgreSQL copy the database from a template database. You can do this by having one DatabaseManager serve as the template for another:>>> template_db = DatabaseManager(initialize_sql=init_db)
>>> class MyTest2(MyTest):
...     resources = [('db', DatabaseManager(template=template_db))]>>> runner.run(MyTest2()) # doctest: +ELLIPSIS
.
...
OK
...transactionintegrationIf the keyword argumendirty_on_commitis True, a DatabaseManager will mark
the database as dirtied after every successfull commit made through thetransactionmodule. This means each test which dirties the database does not
have to manually notify it.>>> man = DatabaseManager(dirty_on_commit=True)If you use this feature, you need to depend on the transaction
(http://pypi.python.org/pypi/transaction) package yourself.Using an existing databaseBy default, van.pg creates a new PostgreSQL cluster in a temporary directory
and launches a PostgreSQL daemon. This works most of the time, but is not very
fast.If you have an already running PostgreSQL cluster, you can tell van.pg to use
it by setting the environment variable VAN_PG_HOST. For example, to run
van.pg’s tests against a local PostgreSQL server with it’s sockets in
/tmp/pgcluster do:$ VAN_PG_HOST=/tmp/pgcluster python setup.py testWARNING: any databases starting with test_db in the target database are likely
to be dropped.Closing ConnectionsBe careful to properly close all connections to the database once your test is
done with it. PostgreSQL doesn’t allow dropping databases while there are open
connections. This will cause van.pg to error when trying to drop the test
database.Programatically creating a clusterAt a lower level, you can also programmatically manipulate your own PostgreSQL cluster.Initialize the Cluster:>>> from van.pg import Cluster
>>> cluster = Cluster()
>>> cluster.initdb()Which creates a database in a temporary directory:>>> import os
>>> dbdir = cluster.dbdir
>>> 'PG_VERSION' in os.listdir(dbdir)
TrueStart it:>>> cluster.start()Create/Test a database:>>> dbname = cluster.createdb()We can connect to the database:>>> import psycopg2
>>> conn = psycopg2.connect(database=dbname, host=cluster.dbdir)
>>> cur = conn.cursor()Twiddle the database to make sure we can do the basics:>>> cur.execute("CREATE TABLE x (y int)")
>>> cur.execute("INSERT INTO x VALUES (1)")
>>> conn.commit()
>>> cur.execute("SELECT * from x")
>>> cur.fetchall()[0][0]
1Stop the cluster daemon:>>> conn.close()
>>> cluster.stop()Start it again:>>> cluster.start()
>>> conn = psycopg2.connect(database=dbname, host=cluster.dbdir)
>>> cur = conn.cursor()
>>> cur.execute("SELECT * from x")
>>> cur.fetchall()[0][0]
1And cleanup:>>> conn.close()
>>> cluster.cleanup()
>>> cluster.dbdir is None
True
>>> os.path.exists(dbdir)
FalseDevelopmentDevelopment takes place on GitHub:http://github.com/jinty/van.pgCHANGES2.0 (unreleased)Support Python 3.2.Drop Python 2.5 support.Add tox.ini for testing against multiple python versions.Run PostgreSQL as a subprocess rather than as a daemon (via pg_ctl).Re-organize code to improve reuse and test coverage.