title: Jest coverage ignore
body: <p>I'm trying to ignore a couple of files from my code coverage output.  On reading the docs <a href="https://facebook.github.io/jest/docs/configuration.html#coveragepathignorepatterns-array-string" rel="noreferrer">coveragePathIgnorePatterns</a> it looks like I can ignore folders.</p>
  
  <p>I'm trying to ignore <strong>dummy</strong> and <strong>helpers</strong> folders from my coverage, but they seem to always be included:</p>
  
  <p>Jest config:</p>
  
  <pre><code>{
    "browser": true,
    "collectCoverageFrom": ["&lt;rootDir&gt;/src/**/*.{js,jsx}", "!&lt;rootDir&gt;/__tests__/__dummy__/test.js"],
    "coveragePathIgnorePatterns": ["&lt;rootDir&gt;/node_modules/", "&lt;rootDir&gt;/__tests__/__helpers__/", "&lt;rootDir&gt;/__tests__/__dummy__/"],
    "roots": [
      "&lt;rootDir&gt;/__tests__/",
      "&lt;rootDir&gt;/src/"
    ],
    "modulePaths": [
      "&lt;rootDir&gt;/src/"
    ],
    "modulePathIgnorePatterns": [
      "&lt;rootDir&gt;/lib/",
      "&lt;rootDir&gt;/node_modules/",
      "&lt;rootDir&gt;/__tests__/__helpers__/",
      "&lt;rootDir&gt;/__tests__/__dummy__/"
    ],
    "setupTestFrameworkScriptFile": "@djforth/jest-matchers",
    "testPathIgnorePatterns": [
      "&lt;rootDir&gt;/__tests__/__dummy__",
      "&lt;rootDir&gt;/__tests__/__dummy__",
      "&lt;rootDir&gt;/lib",
      "&lt;rootDir&gt;/node_modules",
      "&lt;rootDir&gt;/bower_components"
    ],
    "verbose": true
  }
  </code></pre>
  
  <p>I get the following report:</p>
  
  <pre><code>-----------------------|----------|----------|----------|----------|----------------|
  File                   |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
  -----------------------|----------|----------|----------|----------|----------------|
  All files              |    98.87 |    96.48 |     92.5 |    99.55 |                |
   __helpers__           |    84.21 |      100 |    54.55 |    90.91 |                |
    test.js              |    84.21 |      100 |    54.55 |    90.91 |              6 |
   __tests__/__helpers__ |      100 |      100 |      100 |      100 |                |
    create_spy_obj.js    |      100 |      100 |      100 |      100 |                |
   src                   |      100 |       80 |     87.5 |      100 |                |
    index.js             |      100 |       80 |     87.5 |      100 |                |
   src/utils             |      100 |    97.73 |      100 |      100 |                |
    compile_spies.js     |      100 |    81.82 |      100 |      100 |                |
    create_callbacks.js  |      100 |      100 |      100 |      100 |                |
    create_spies.js      |      100 |    97.44 |      100 |      100 |                |
    create_stubs.js      |      100 |      100 |      100 |      100 |                |
    get_spy.js           |      100 |      100 |      100 |      100 |                |
    merger.js            |      100 |      100 |      100 |      100 |                |
    reset_spies.js       |      100 |      100 |      100 |      100 |                |
    title_keys.js        |      100 |      100 |      100 |      100 |                |
  -----------------------|----------|----------|----------|----------|----------------|
  </code></pre>