Require your devtools snippets in your devtools snippets.

devtools_require_snippets.js

window.__modules__ = {}
window.require = require

var modules = window.__modules__

Promise
  .resolve()
  .then(get_snippets)
  .then(deserialize)
  .then(function(snippets){
    snippets.map(function(module){define(module.name, module.content)})
  })


function require(id) {
  if(!modules[id]) throw new Error(id + ' module not yet defined')
  if(typeof modules[id] === "string") return modules[id] = eval(modules[id])
  return modules[id]
}


function define(id, string) {
  if(modules[id]) throw new Error(id + ' module or property already exists')
  return modules[id] = string
}


function deserialize(string){
  if(typeof string !== "string") throw Error("deserialize needs a string")
  if(string === "") throw Error("no snippets present")
  return JSON.parse(string)
}


function get_snippets(){
  var deferred = Promise.defer()

  InspectorFrontendHost.getPreferences(function(prefs){
    deferred.resolve(prefs.scriptSnippets)
  })

  return deferred.promise
}
// derp snippets require inspired by 
// https://gist.github.com/gordonbrander/3861744

devtools_require_snippets.min.js

function require(id){if(!modules[id])throw Error(id+" module not yet defined");return"string"==typeof modules[id]?modules[id]=eval(modules[id]):modules[id]}function define(e,r){if(modules[e])throw Error(e+" module or property already exists");return modules[e]=r}function deserialize(e){if("string"!=typeof e)throw Error("deserialize needs a string");if(""===e)throw Error("no snippets present");return JSON.parse(e)}function get_snippets(){var e=Promise.defer();return InspectorFrontendHost.getPreferences(function(r){e.resolve(r.scriptSnippets)}),e.promise}window.__modules__={},window.require=require;var modules=window.__modules__;Promise.resolve().then(get_snippets).then(deserialize).then(function(e){e.map(function(e){define(e.name,e.content)})});

harness.js

function test(msg, f){
  console.log(msg)
  f({
    ok: (expr, msg) => expr ? console.log("pass: "+msg) : console.log("fail: "+msg)
  })
}


test("should be true", t => {
    t.ok(true, "istrue")
})


// devtools export
;({
  test
})

main.js

var test = require("harness") //this is the name of the snippet

Important:

Open Inspector (ctrl+shift+I)
Undock Inspector in Seperate Window
Inspect Inspector (ctrl+shift+i)
Load the require script.

Last Value in a snippet will be the "export"