Database rollback fixtures in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of a database rollback fixture in pytest?

A database rollback fixture ensures that any changes made to the database during a test are undone after the test finishes. This keeps the database clean and consistent for other tests.

beginner

How does a rollback fixture help maintain test isolation?

By rolling back database changes after each test, the fixture prevents one test's data from affecting another test, ensuring tests run independently and reliably.

intermediate

Which pytest fixture scope is commonly used for database rollback fixtures and why?

The 'function' scope is commonly used because it rolls back changes after each test function, ensuring a fresh database state for every test.

intermediate

Example snippet: How do you start a transaction and rollback after a test using pytest fixtures?

Use a fixture that begins a transaction before the test and rolls it back after. For example:<br>

@pytest.fixture
 def db_rollback(db_session):
     db_session.begin()
     yield db_session
     db_session.rollback()

intermediate

Why is it better to use rollback fixtures instead of manually cleaning the database after tests?

Rollback fixtures are faster and less error-prone because they undo changes automatically within a transaction, avoiding complex cleanup code and reducing test flakiness.

What does a database rollback fixture do in pytest?

A Deletes the entire database

B Reverts database changes after each test

C Commits database changes permanently

D Creates a new database for each test

A rollback fixture reverts any database changes made during a test to keep the database clean.

Which pytest fixture scope is best for database rollback to isolate tests?

A module

B session

C function

D class

The 'function' scope runs the fixture for each test function, ensuring isolation.

Why use transactions with rollback in tests?

A To undo changes automatically after tests

B To keep database changes permanent

C To speed up database queries

D To backup the database

Transactions allow changes to be undone automatically by rolling back after tests.

What happens if you don't rollback database changes after tests?

A Tests may interfere with each other

B Tests run faster

C Database stays clean

D Database size decreases

Without rollback, leftover data can cause tests to affect each other, causing failures.

In pytest, how do you ensure a rollback happens after a test?

A Restart the database server

B Call commit() after test

C Delete database manually

D Use yield in fixture and rollback after yield

Using yield in a fixture lets you run rollback code after the test finishes.

Explain how a database rollback fixture works in pytest and why it is important for test reliability.

Think about how transactions can undo changes automatically.

Describe the steps to create a pytest fixture that rolls back database changes after each test function.

Use yield in the fixture to separate setup and teardown.