Django-like unit testing database in plain python

Question

I have a python project that uses Postgresql. I would like to use django-like unit tests where the database is created and destroyed at every test. However, I don't want to use sqlalchemy. I tried something along these lines:

pg = psycopg2.connect(
"host={} dbname={} user={} password={}".format(
POSTGRES_HOST, 'postgres', POSTGRES_USER, POSTGRES_PASSWORD))

pg.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)
cur = pg.cursor()




def reset_db():
    cur.execute('DROP DATABASE IF EXISTS {} '.format(POSTGRES_DB))
    cur.execute('CREATE DATABASE {}'.format(POSTGRES_DB))

    newconn = psycopg2.connect(
    "host={} dbname={} user={} password={}".format(
    POSTGRES_HOST, POSTGRES_DB, POSTGRES_USER, POSTGRES_PASSWORD))

    newcur =  newconn.cursor()

    # SCHEMAS is an imported dict containing schema creation instructions
    for schema in SCHEMAS:
        newcur.execute(SCHEMAS[schema])

    return newcur

class Test(TestCase):
    def setUp(self):
        os.environ['testing'] = 'true'
        self.cur = reset_db()

Then the setUp method sets an environmental variable that informs my database layer to use the testing db.

This seems to work fine. The only problem is the reset_db() takes about 0.8 seconds, which is far too much.

Are there better approaches or ways to optimise my approach?

kristaps · Accepted Answer · 2018-06-28 10:08:29Z

1

You could try what Django is doing - start a transaction before each test and roll it back after, undoing any DB changes made during the test.

answered Jun 28, 2018 at 10:08

kristaps

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2 Comments

RobatStats Over a year ago

This would be the best option, but Is there a way to make this work even if not all the code uses the same db connection?

kristaps Over a year ago

That would require a wrapper transaction on each connection, but that should be relatively easy once you have the single connection mechanism figured out.

Enthusiast Martin · Accepted Answer · 2018-06-28 10:01:29Z

1

Recreating DB after each test case is quite expensive operation.

Perhaps, creating your DB once at the beginning and then only deleting all data from all tables after each test case would be one of possible solutions ?

answered Jun 28, 2018 at 10:01

Enthusiast Martin

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