failing.js

require.config({
    paths: {
        "my-plugin": "./my-plugin"
    }
});

define("my-plugin", []);

define(["my-plugin!./test.css"], function (r) {
  console.log(r)
})

index.html

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>GistRun</title>
</head>
<body>
  <h1>Hello world!</h1>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/require.js/2.3.3/require.js" data-main="failing"></script>
  <!--<script src="./text.js"></script>-->
</body>
</html>

my-plugin.js

define("my-plugin", function (input) {
  return {
    normalize: function (i) {
      return i;
    },
    load: function (name, req, onLoad, config) {
      return onLoad("some content");
    }
  }
})