## 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

```text
(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/pst_gIS8TpYJ1Iyb_fT5nxqCJg