What's so "test" about this bowl?
I never get the glaze exactly horizontal where one glaze meets the next. A new(ish) potter asked me how to do that, and I said I am unsuccessful at it. And I actually usually like that so it proves a human hand and eye made this.
No, the test being carried out on the bowl here is that it has a rolled lip. It may well have some air inside the roll, and I expected it wouldn't stay together. But it did. And it feels really nice, being light to handle though it looks very sturdy.