Which distribution are you using? According to Ubuntu's run-parts manual:
If neither the --lsbsysinit option nor the --regex option is given then the names must consist entirely of ASCII upper- and lower-case letters, ASCII digits, ASCII underscores, and ASCII minus-hyphens.
 Therefore run-parts won't run a script named test.bash.  Thanks to this rule, you can avoid to accidentally run scripts renamed toscripts, for example *.old, or *.dpkg-dist or *.dpkg-old onby dpkg upgrades.
 
                