Test Data Management — Fixtures, Factories, and Isolation
Master test data with fixtures, factory functions, database seeding, test isolation strategies, and cleanup patterns.
You wrote a beautiful test. It creates a user, creates an order for that user, and verifies the order total is correct. It passes. You run the suite again. It fails. Why? Because the user from the first run still exists in the database, and the unique email constraint blocks the second run.
Test data management is the unglamorous foundation that makes tests reliable. Without it, tests are flaky, coupled, and break in mysterious ways. With it, every test run starts clean and produces consistent results.
The Core Principles
1. Tests Must Be Independent
No test should depend on the state left behind by another test. If Test B only passes after Test A runs, you have a hidden dependency that will eventually break.
2. Tests Must Be Repeatable
Running the same test 100 times sho
This lesson is part of the Guild Member curriculum. Plans start at $29/mo.