dh_testversion - ensure that the correct version of debhelper is installed
dh_testversion [debhelper options] [operator] [version]
Note: This program is deprecated. You should use build dependencies instead.
dh_testversion compares the version of debhelper against the version you specify, and if the condition is not met, exits with an error message.
You can use this in your debian/rules files if a new debhelper feature is introduced, and your package requires that feature to build correctly. Use debhelper's changelog to figure out the version you need.
Be sure not to overuse dh_testversion. If debhelper version 9.5 introduces a new dh_autofixbugs command, and your package uses it, then if someone tries to build it with debhelper 1.0, the build will fail anyway when dh_autofixbugs cannot be found, so there is no need for you to use dh_testversion.
This program is a part of debhelper.
Joey Hess <email@example.com>