On Tue, Oct 17, 2017 at 4:58 PM, Sam Lee <skyn...@gmail.com> wrote:
> Hi,
>
> I am passing a custom creator to sqlalchemy.create_engine().
> And, I want to simulate the following scenario in automated test without
> using actual database connection:
>
> 1. Request a connection from pool: connects to DB.
> 2. DB goes down.
> 3. Request a connection from pool: connection is invalid.
> 4. Request a connection from pool: connects to DB again.
>
> I'm trying the following testcase:
>
> def mycreator():
> print('called')
> # return psycopg2.connect(....)
> return unittest.mock.MagicMock()
>
> engine = create_engine('postgresql://', creator=mycreator,
> pool_size=1)
> c = engine.connect() # calls mycreator
> c.close() # connection returned to pool
> c = engine.connect() # does not call mycreator (reuses connection
> in pool)
> c.invalidate()
> c.close()
> c = engine.connect() # calls mycreator (because connection is
> invalidated)
>
>
> But, it throws exception because MagicMock isn't cursor or connection.
I'm assuming you are getting this error from psycopg2 itself. To
use create_engine(), you'd need to mock whatever is being called that
is not compatible, which here I am assuming are things like
psycopg2.extensions.register_type,
psycopg2.extras.register_default_json, and others. Patch these with
mocks so that they have no effect.
However, if your test is just looking for the behavior of the pool,
then test against a QueuePool directly.
The tests in test/engine/test_reconnect.py make extensive use of mocks
to simulate disconnects though most of the create_engine() integration
is done using real database connections with a patch to close out the
DBAPI connection to simulate a disconnect.
> What kind of mock or fake connection object should mycreator return in the
> test
> so that above snippet will behave as I expect it to, calling mycreator
> twice?
> (Using actual connection, psycopg2.connect(), works as expected).
>
> Thanks.
> Sam
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
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http://www.sqlalchemy.org/
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