Running tests depending on esri-leaflet headlessly

I’m writing a plugin that uses Leaflet and Esri-Leaflet. For my plugin, I have a reasonably large suite of unit tests powered by Mocha, Chai, Sinon, etc. My plugin is structured as a series of ES6 modules.

In my unit tests, I import { FeatureLayerService } from 'esri-leaflet', but this causes the tests to break because esri-leaflet depends on leaflet, which depends upon a global window resulting in a ReferenceError: window is not defined error in a headless environment like Node. I’ve been able to use pieces of Leaflet itself in my tests thanks to the leaflet-headless package, which sort of hacks over the global window dependency and allows me to import { Map } from 'leaflet-headless' and the like.

My question is: because esri-leaflet has depends on leaflet and not leaflet-headless (and it obviously should), is there any way to allow my unit tests to run, perhaps by:

1. Forcing esri-leaflet to resolve the leaflet dependency to leaflet-headless (I’m transpiling with Babel and Webpack is my bundler)
2. Polyfilling/stubbing the window global (I’ve explored this some using jsdom with no luck)
3. Ejecting/removing the leaflet dependency from esri-leaflet (not likely since there are obvious dependencies)
4. Another option I haven’t thought of

• Version of Leaflet (L.version): 1.1.0, 1.0.3

• Version of esri Leaflet (L.esri.VERSION): 2.0.8

Code I want to work:

// inside a unit spec
import { Map } from 'leaflet-headless'; // works fine
import { FeatureLayerService } from 'esri-leaflet'; // throws

Resulting errors:

ReferenceError: window is not defined
    at Object.<anonymous> (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/leaflet/dist/leaflet-src
.js:13250:3)
    at Module._compile (module.js:570:32)
    at Module._extensions..js (module.js:579:10)
    at Object.require.extensions.(anonymous function) [as .js] (/mnt/c/dev/Leaflet.Control.NestedLayers/
node_modules/babel-register/lib/node.js:152:7)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)
    at L$1__default (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/esri-leaflet/dist/esri-leaflet
-debug.js:5:82)
    at Object.<anonymous> (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/esri-leaflet/dist/esri-l
eaflet-debug.js:8:2)
    at Module._compile (module.js:570:32)
    at Module._extensions..js (module.js:579:10)
    at Object.require.extensions.(anonymous function) [as .js] (/mnt/c/dev/Leaflet.Control.NestedLayers/
node_modules/babel-register/lib/node.js:152:7)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/mnt/c/dev/Leaflet.Control.NestedLayers/src/Leaflet.LayerHierarchy.MapServerP
arser.js:10:1)
    at Module._compile (module.js:570:32)
    at loader (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/babel-register/lib/node.js:144:5)
    at Object.require.extensions.(anonymous function) [as .js] (/mnt/c/dev/Leaflet.Control.NestedLayers/
node_modules/babel-register/lib/node.js:154:7)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/mnt/c/dev/Leaflet.Control.NestedLayers/test/Leaflet.LayerHierarchy.MapServer
Parser.spec.js:2:1)
    at Module._compile (module.js:570:32)
    at loader (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/babel-register/lib/node.js:144:5)
    at Object.require.extensions.(anonymous function) [as .js] (/mnt/c/dev/Leaflet.Control.NestedLayers/
node_modules/babel-register/lib/node.js:154:7)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)
    at /mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/mocha/lib/mocha.js:230:27
    at Array.forEach (native)
    at Mocha.loadFiles (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/mocha/lib/mocha.js:227:14)
    at Mocha.run (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/mocha/lib/mocha.js:495:10)
    at loadAndRun (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/mocha/bin/_mocha:426:22)
    at rerun (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/mocha/bin/_mocha:454:5)
    at /mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/mocha/bin/_mocha:462:7
    at StatWatcher.<anonymous> (/mnt/c/dev/Leaflet.Control.NestedLayers/node_modules/mocha/lib/utils.js:
196:9)
    at emitTwo (events.js:106:13)
    at StatWatcher.emit (events.js:191:7)
    at StatWatcher._handle.onchange (fs.js:1501:10)

npm ls | grep leaflet:

├── chai-leaflet@0.0.12
├─┬ esri-leaflet@2.0.8
│ ├── leaflet-virtual-grid@1.0.4
├── leaflet@1.0.3
├─┬ leaflet-headless@0.2.5
│ └─┬ leaflet-image@0.4.0

[colbin8r]

@jgravois I also didn’t realize that Karma could run tests in PhantomJS… my mistake! PhantomJS is the closest thing to a headless browser I know of (the goal of the project IIRC). I’ll look into using Karma. Sorry for the misunderstanding, @jgravois!

[jgravois]

i’m going to go ahead and close this issue as there’s nothing actionable for esri-leaflet at the moment, but i’d be more than happy to discuss the issue further and/or talk about changes in this repo down the line if anyone can recommend something.