When you run tests in a random class and method order, which results in them failing, you have demonstrated test pollution. This is usually the result of sloppy tests that don’t clean up after themselves. Taking the time to understand the failures can help point you towards the root cause of pollution. Recipients of pollution are either Beneficiaries or Innocent Bystanders.
Beneficiaries Beneficiaries are those tests that originally took advantage of test pollution, baking it into the assumptions used to write the test.