test: add extra test case for issue 7590
test: add extra test case for issue 7590

LGTM=iant
R=iant
CC=golang-codereviews
https://codereview.appspot.com/78040043

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang