title: Jest Could not locate module FileName.css (mapped as identity-obj-proxy)
body: <p>I've been trying to set up a testing environment for my React project and I had a problem with Unexpected token when importing the CSS file. i added the moduleNameMapper to the package.json to fix it and now i'm facing this issue.
  Does anyone know what can i do to fix this? </p>
  
  <pre><code>&gt; myProject@0.0.1 test C:\Users\admin\Documents\myApp
  &gt; jest
  
  FAIL _tests_\Home.test.js
    ● Test suite failed to run
  
      Configuration error:
  
      Could not locate module react-datepicker/dist/react-datepicker-cssmodules.css (mapped as identity-obj-proxy)
  
      Please check:
  
      "moduleNameMapper": {
        "/^.+\.(css|less)$/": "identity-obj-proxy"
      },
      "resolver": undefined
  
  Test Suites: 1 failed, 1 total
  Tests:       0 total
  Snapshots:   0 total
  Time:        1.894s
  Ran all test suites.
  npm ERR! Test failed.  See above for more details.
  </code></pre>
  
  <p>jest portion of package.json</p>
  
  <pre><code>  "jest": {
      "transform": {
        "^.+\\.jsx?$": "babel-jest"
      },
      "moduleNameMapper": {
        "\\.(s?css|less)$": "identity-obj-proxy"
      }
    },
  </code></pre>