[docs] Add test docs how to use custom facter/puppet version

diff --git a/README b/README
index e08cc5bc0ab05c61d2f5e2b7d10e483ebc2bdf76..410201dcb60189a5fdf1e4254c84aa09b63dd1d2 100644 (file)
--- a/README
+++ b/README
@@ -576,6 +576,10 @@ To run pupept rspec tests:
     bundle install --path vendor/bundle
     bundle exec rake spec
 
+Using different facter/puppet versions:
+
+    FACTER_GEM_VERSION=1.6.10 PUPPET_GEM_VERSION=2.7.23 bundle install --path vendor/bundle
+    bundle exec rake spec
 
 Licensing
 =========