Find the true file names of files in ruby on windows

I have a list of files for a Ruby script to process. The script always run on an Windows PC. How can the script find the actual name?

Example:

File List -> Actual file on disk 
TEST.TXT  -> test.txt
TeSt.TxT  -> test.txt

After more testing I found that :

puts File.absolute_path("./TEST.RB")
puts Dir["./TEST.RB*"].first
#Path as on disk
puts File.absolute_path("./../Vdd/TEST.RB")
puts Dir["./../Vdd/TEST.RB*"].first
#Path case not as on disk
puts File.absolute_path("./../vdd/TEST.RB")
puts Dir["./../vdd/TEST.RB*"].first

Outputs

C:/Projects/xcms/software-HEAD/build/tools/Vdd/test.rb
./test.rb
C:/Projects/xcms/software-HEAD/build/tools/Vdd/test.rb
./../Vdd/test.rb
C:/Projects/xcms/software-HEAD/build/tools/vdd/test.rb
./../vdd/test.rb

So both realpath does nothing while absolute_path and Dir["#{file}*"].first gets the file name correct but not the path name.