This is the normal way that Duo tests would be created for modules. It's testing the logic inside the module itself, but it's not testing the actual "built" file.

component.json

{
  "name": "to-slug-case",
  "dependencies": {
    "ianstormtaylor/to-no-case": "1.x"
  },
  "development": {
    "component/assert": "0.x"
  }
}

index.js

var clean = require('ianstormtaylor/to-no-case');

module.exports = function(input){
  return clean(input).replace(/ /g, '-');
}

Makefile

build-test.js: index.js test.js
  duo test.js > build-test.js
  
test: build-test.js
  mocha build-test.js

test.js

var slug = require('..');
var assert = require('component/assert');

// Tests here...