Very handy. My previous simple test-case was simply a selection from this well-known text-file which is simply a collection of somewhat uncommon unicode characters, usually used for rendering tests.
But this set of strings is specifically designed to cause edge-case errors.
Also don't forget Spolsky's seminal "The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)".
https://www.cl.cam.ac.uk/~mgk25/ucs/examples/UTF-8-demo.txt
But this set of strings is specifically designed to cause edge-case errors.
Also don't forget Spolsky's seminal "The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)".
https://www.joelonsoftware.com/2003/10/08/the-absolute-minim...