title: What are the differences between the commands: spec, rspec, rake spec?
body: <p>Here is a thread I looked at:</p>
  
  <p><a href="https://stackoverflow.com/questions/6116668/rspec-how-to-run-a-single-test">rspec how to run a single test?</a></p>
  
  <p>One answer says to use <code>rspec</code> to run tests. Another answer (originally?) said to use <code>rake spec</code> to run tests but then a commenter said it's <code>spec</code> not <code>rake spec</code>.  And I have some notes on using rspec that say:</p>
  
  <pre><code>#RSpec prefix not required if you run your program
  #with `spec` command 
  
  RSpec.describe 'some task' do
    it 'blah blah blah' do
      true
    end
  end
  </code></pre>
  
  <p>I can find no information on the <code>spec</code> command, and it doesn't appear to exist on my system:</p>
  
  <pre><code>$which rspec
  /Users/7stud/.rvm/gems/ruby-2.2.1/bin/rspec
  
  $ which spec
  $ 
  </code></pre>
  
  <p>Is the <code>spec</code> command a rails feature?</p>