alt Hacker NewsThat is a useful pattern, though I was unclear on why `t.Cleanup` and not `defer`. In case others are curious, too:
> Parallel subtestsWith t.Run(..., func(t testing.T) { t.Parallel(); ... }), the parent test function can return (and thus run its defers) before parallel subtests actually finish.*
Short version is this:
If you are going to get into the business of introducing order dependence to test cases through global state (see my other reply on the parent), you will always want the cleanup to work correctly.
1. Using (testing.TB).Cleanup is a good defensive habit to have if you author test helpers, especially if the test helpers (see: (testing.TB).Helper) themselves do something (e.g., resource provisioning) that requires ordered teardown. Using (testing.TB).Cleanup is better than returning a cancellation or cleanup function from them.
2. (testing.TB).Cleanup has stronger guarantees about when it is called, especially when the test case itself crashes. Example: https://go.dev/play/p/a3j6O9RK_OK.
I am certain that I am forgetting another edge case or two here.
Generally nobody should be designing their APIs to be testable through mutable global state. That solves half the problem here.