database transaction rollback between tests: how to set up

TL;DR

Wrap each test in a database transaction and roll it back. It is the fastest isolation strategy; configure it in the test framework's setup hooks.

Error

(Not an error; a setup guide. The failure it prevents: data leaking between tests.)

Steps

1. Enable the framework's transactional mode (RSpec transactional fixtures, Django TestCase, Spring @Transactional). Expected: the option on.
2. Verify: insert a row in one test, assert absence in the next. Expected: rollback proven.
3. For raw setups, open the transaction in beforeEach and roll back in afterEach. Expected: manual but explicit.
4. Exclude multi-connection tests (browser-driven) to truncation strategy. Expected: the exception handled.
5. Run the suite twice. Expected: second run green.

When to use

• Configuring DB isolation.
• You want the fastest correct strategy.

When not to use

• Tests using a separate DB connection (use truncation).
• Non-relational stores without transactions.

Tool compatibility

• RSpec, Django, Spring, and equivalents.

Variant phrasings

Transactional tests setup

The general task.

Rollback database after each test

The mechanism; framework hooks.

Why it happens

Rollback is O(1) cleanup versus O(n) deletion. It is faster and atomic.

Edge cases

• Some DDL cannot roll back; keep migrations out of tests.
• Savepoints nest transactions for complex setups.
• Parallel tests need separate databases regardless.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstgIS8TpYJ1IybfT5nxqCJg