title: How do I check that all the dependencies of my installed Ruby gems are satisfied?
body: <p>I must be missing something because last night I was astonished to find that googling for <code>check gem dependencies</code> and similar didn't reveal the answer for this.</p>
  
  <p>I'm basically after a rough equivalent of <code>rpm -V</code> - a command that will go through some or all my installed gems and make sure that their dependencies are also installed.  Since <code>gem install</code> by default installs any dependent gems, normally this is not necessary; however, if you <code>gem uninstall</code> a gem and tell it to proceed with the uninstall even though other gems depend on the one being uninstalled, then obviously you will end up with broken dependencies.  The question is, how do you then list those broken dependencies without installing / uninstalling / updating any gems?</p>
  
  <p>N.B. answers which involve Bundler are not much use to me, since I'm still stuck on Rails 2.x for various reasons.</p>