Right on, thanks.
Their specific question was “how are the tests being defined here?” and I was confused as I did not realize that they could not see them, plus they were on the platform. The answer, I suppose, is “the maintainers write them” but that did not seem very helpful, along with the confusion of not realizing that they may not have seen them at all.
For general clarity, Concept Exercises are not supposed to be solved using the tests as a reference. They are explictely designed so that the instructions and the hints provide the information needed and looking at the tests is likely going to be harmful as the exercises are simple enough that often the test code is the same or very similar to the solution code.
This is different in the Practice Exercises, where we explicitly expect students to use the tests, so we show them in the editor.
I was trying to do “foo * 2” instead of “foo = foo * 2” and that was tripping up one of the tests, which frustrated me as I couldn’t see it. Once I saw the bug in my syntax after my mentor pointed out I didn’t need to do the awkward fix I was using to pass the test.