(This test is currently disabled.)

Name a file "ẛ̣Å.txt" and upload it to each of these forms. This file name (before the extension), in Unicode, is is U+1E9B U+0323 U+212B.

UTF-8 encodings of the file name in various normalisation forms
Original Bytes 
 E1 BA 9B  CC A3            E2 84 AB
NFD bytes 
 C5 BF     CC A3  CC 87     C3 85
NFC bytes 
 E1 BA 9B  CC A3            C3 85
NFKD bytes 
 73        CC A3  CC 87     C3 85
NFKC bytes 
 E1 B9 A9                   C3 85

You can create the file on Unix using this command line:

echo -e '\xE1\xBA\x9B\xCC\xA3\xE2\x84\xAB.txt' | xargs touch