Man page doesn't say where to send bugs, unlike all other GNU man pages. Man page says -t --test Test. Check the compressed file integrity. It should also say "and quit" like -V --version Version. Display the version number and compilation options then quit. says.
Also $ gunzip -t file.gz gzip: file.gz: invalid compressed data--crc error gzip: file.gz: invalid compressed data--length error prints extra newlines. $ gunzip -V gzip 1.9