test block with no tests, and test counts

[shriram]

I feel like we've been over this before, but I can't find the PR right now…

It seems really confusing to use a green background for "no tests" blocks. Students see

and don't read the fine-print and think a bunch of top-level function calls (with no testing operators) is a valid test suite.

Didn't we discuss changing the color of such blocks? If anything, it should be a "negative" color, because more likely than not this is an error (and if it's intentional, the programmer will know — but even then, they may later forget to change the block to contain tests again, so the reminder can't hurt).

I realize there's a fine line here and green for a single test could still obscure similar errors. We should still handle this special case differently because it would be instructive for students. But perhaps instead of a small number amidst a lot of text

we should have a stronger visual indicator of how many tests passed [like this, but even more salient]:

[schanzer]

I'm a big fan of stoplight colors. We already use green for pass and red for fail. Perhaps we should use yellow for this?