A reliable automated test suite should be able to run tests independently, in isolation, and in parallel.
That sounds obvious, but one of the most common causes of unreliable automation is something much less obvious: shared test data.
When multiple tests depend on the same user, student, account, order, or other database entity, the tests are no longer truly independent. One test can influence another, creating failures that have nothing to do with the functionality being tested.
This is known as test pollution.
And once test pollution enters an automation suite, confidence in the results begins to disappear.
