Database rollback fixtures in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a pytest fixture that rolls back database changes after each test.

PyTest

import pytest

@pytest.fixture
 def db_session():
     session = create_session()
     yield session
     session.[1]()

Drag options to blanks, or click blank then click option'

Acommit

Bflush

Cclose

Drollback

Attempts:

3 left

💡 Hint

Common Mistakes

Using commit instead of rollback causes changes to persist.

Using close does not undo changes.

Using flush only sends changes but does not rollback.

The rollback() method undoes all changes made during the test, ensuring a clean state for the next test.

2fill in blank

medium

Complete the code to use the fixture in a test function that queries the database.

PyTest

def test_user_count(db_session):
     count = db_session.query(User).count()
     assert count [1] 0

Drag options to blanks, or click blank then click option'

A==

B>=

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using > or >= may pass if users exist, but test expects empty.

Using != may allow unexpected counts.

Using < is incorrect for count checks.

The test asserts that the user count is exactly zero, assuming a clean database state after rollback.

3fill in blank

hard

Fix the error in the fixture to ensure the session is properly closed after rollback.

PyTest

@pytest.fixture
def db_session():
    session = create_session()
    yield session
    session.rollback()
    session.[1]

Drag options to blanks, or click blank then click option'

Acommit()

Bflush()

Cclose()

Drefresh()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling commit after rollback is contradictory.

Flush does not close the session.

Refresh reloads objects but does not close session.

Calling close() after rollback properly releases database resources.

4fill in blank

hard

Fill both blanks to create a fixture that starts a transaction and rolls it back after the test.

PyTest

@pytest.fixture
def transactional_db():
    connection = engine.connect()
    transaction = connection.[1]()
    session = Session(bind=connection)
    yield session
    session.[2]()
    transaction.rollback()
    connection.close()

Drag options to blanks, or click blank then click option'

Abegin

Bcommit

Crollback

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using rollback to start transaction is incorrect.

Not committing session before rollback can cause errors.

Closing connection before rollback causes errors.

The transaction is started with begin() and the session commits changes before rollback to ensure proper cleanup.

5fill in blank

hard

Fill all three blanks to implement a fixture that uses savepoint for nested rollback.

PyTest

@pytest.fixture
def savepoint_db():
    connection = engine.connect()
    transaction = connection.begin()
    savepoint = connection.[1]()
    session = Session(bind=connection)
    yield session
    session.[2]()
    savepoint.[3]()
    transaction.rollback()
    connection.close()

Drag options to blanks, or click blank then click option'

Abegin_nested

Bcommit

Crollback

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using rollback to create savepoint is wrong.

Not rolling back savepoint causes changes to persist.

Closing connection before rollback causes errors.

The savepoint is created with begin_nested(). The session commits changes, then the savepoint rolls back, and finally the transaction rolls back to clean up.