title: No coverage data with `nyc mocha`
body: <p>Although my tests run perfectly fine with</p>
  
  <pre><code>$ cross-env NODE_ENV=test nyc --require babel-register mocha
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/Z1hnw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Z1hnw.png" alt="enter image description here"></a></p>
  
  <p>Everything is zero, and inside the <code>./coverage</code> dir there is no coverage  info too :(</p>
  
  <p>My project is very basic (ES2015):</p>
  
  <pre><code>./lib.js
  ./test/lib.spec.js
  </code></pre>
  
  <p>Here is my <code>.babelrc</code>:</p>
  
  <pre><code>{
    "presets": [
      "es2015",
      "stage-0"
    ],
    "plugins": [
      "transform-decorators-legacy",
      "transform-class-properties"
    ],
    "env": {
      "test": {
        "plugins": [
          "istanbul"
        ]
      }
    }
  }
  </code></pre>
  
  <p>and the <code>.nycrc</code> file</p>
  
  <pre><code>{
    "check-coverage": false,
    "lines": 99,
    "statements": 99,
    "functions": 99,
    "branches": 99,
    "include": [
      "./lib.js"
    ],
    "reporter": [
      "lcov",
    "text-summary"
    ],
    "require": [],
    "extension": [
      ".js"
    ],
    "cache": false,
    "all": false,
    "report-dir": "./coverage"
  }
  </code></pre>
  
  <p>I've also made an identical setup using ES5 only with the same result. Any suggestions why I have no coverage ?</p>
  
  <p>UPDATE: Solution can be found <a href="https://github.com/istanbuljs/nyc/issues/624" rel="nofollow noreferrer">here</a></p>