Using a symbol for `:environment_id` is causing an intermittent issue on Ruby 1.8 during the Hash#merge as we're ending up with both a string and symbol in the attributes hash (host.attributes returns strings as keys):

<pre>[7] pry(#<PuppetclassesControllerTest>)> host.attributes.merge!(:environment_id => environments(:global_puppetmaster).id)[:environment_id]
=> 153855663
[8] pry(#<PuppetclassesControllerTest>)> host.attributes.merge!(:environment_id => environments(:global_puppetmaster).id)["environment_id"]
=> 334344675
</pre>

I'd switch it to a string 'environment_id'