I think your last sentence needs to go first. Quote your variables! There's no actual footgun in the specification of the test builtin -- the footgun is shell i

I think your last sentence needs to go first. Quote your variables! There's no actual footgun in the specification of the test builtin -- the footgun is shell itself. The behaviour that you mention makes sense because [ "$FOO" ] is always the non-empty check regardless what it contains (could be "-n").