fnmatch(pattern, *args) -> bool[permalink][rdoc]File.fnmatch(pattern, self.to_s, *args) と同じです。
例
require "pathname"
path = Pathname("testfile")
path.fnmatch("test*")                       # => true
path.fnmatch("TEST*")                       # => false
path.fnmatch("TEST*", File::FNM_CASEFOLD)   # => true
[SEE_ALSO] File.fnmatch