title: before hook before all test cases in Mocha
body: <p>I have a "before" hook that I want to run before all test cases(files), the ideal situation would be run it once and only once no matter how many test cases and which test case I run. </p>
  
  <p>Now what I do is putting that "before" hook in a separate file, and do "require("../beforeAll.js")"  in the beginning of every test file, </p>
  
  <pre><code>//beforeAll.js
  before('description', function(done) {
      //do something
      done()
  }
  
  
  //all test files
  require('../beforeAll.js')
  //test 
  //......
  </code></pre>
  
  <p>which I think will run the "before" hook every time a test file runs, but I don't know better way to do it. However, when I run all the test cases, the "before" hook actually runs only once. </p>
  
  <p>So my question are, why the "before" hook runs only once? What is the best way to do it in this scenario(only run once)?</p>