title: Rails could not find gem
body: <p>when tried to start server <code>rails s</code> i have got  </p>
  
  <pre><code> Could not find minitest-5.9.0 in any of the sources
      Run `bundle install` to install missing gems.
  </code></pre>
  
  <p>i did <code>gem install minitest -v 5.9.0</code></p>
  
  <p>Successfully installed minitest-5.9.0</p>
  
  <p>1 gem installed</p>
  
  <p>also <code>gem list</code></p>
  
  <pre><code>minitest (5.9.0, 4.7.5)
  </code></pre>
  
  <p>but when i try <code>rails s</code> again i received the same error.</p>
  
  <p>How could i fix it?</p>