Fixtures should own the state they create and clean up reliably. Isolation prevents one test’s writes from changing another test’s assumptions.
Before you start
You should understand inputs, expected outputs and the boundaries of the component under test. State the risk a test should detect before choosing a tool or mock. Distinguish controlled dependencies from real integrations so the result does not imply more coverage than the test actually provides.
The practical goal is to reason through this situation: Use a fresh account and transaction boundary for each persistence test. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Create independent state
Each test gets records or resources it can safely modify.
Step 2: Register cleanup early
Risky setup and failed assertions must not bypass release.
Step 3: Verify no cross-test dependence
Repeated or reordered execution should not change expectations.
Worked scenario
Use a fresh account and transaction boundary for each persistence test.
Two tests share an account; one deletes it while another assumes it exists. Fresh per-test data or a justified transaction isolation strategy removes that order dependency. Cleanup must run after failure as well as success, and should not delete another concurrent test’s records.
Common mistake
Shared mutable records create order-dependent assertions.
Verify the behavior
Force setup and assertion failures and verify owned resources are still released.
Interview exercise
Design cleanup for failure.
Answer and reasoning
Register cleanup before risky operations and ensure it runs after failed assertions as well as successful tests.
Continue learning
Compare the scenario with the Software Testing interview questions and test your understanding with the Software Testing MCQs. For terminology and implementation details, consult the reference material.