clean-up: break filterRequest out into more functions

[groovecoder]

Probably into a new module, and then write tests.

[groovecoder]

I've broken some functions out, but I'm having trouble writing tests for background.js because it uses DOM/Web APIs that I guess aren't available in node? E.g.,

lcrouch:blok lcrouch$ ./node_modules/.bin/tape tests/test-background.js
/Users/lcrouch/code/blok/js/background.js:6
var testpilotPingChannel = new BroadcastChannel(TESTPILOT_TELEMETRY_CHANNEL)
                               ^

ReferenceError: BroadcastChannel is not defined

@rpl - any advice on how to test these bits?

[rpl]

@groovecoder yep,there are at least two strategies that we can use:

inject the dependency explicitly

we can rewrite the module so that any code that uses the BroadcastChannel is inside a function that took the window object as a parameter, e.g.:

exports.backgroundEntryPoint = function({BroadcastChannel}) {
...
}

the real background script will call the function with the background window object as a parameter,
the test will pass an object with a mock/shim/spy BroadcastChannel, e.g.:

node global global

In node you can define new globals by adding them to the global global, eg.:

global.BroadcastChannel = function(...args) {
  this._initArgs = args;
}

// require the module that needs the global after the needed global is defined
var {anExportedFunctionToTest} = require('../js/module-that-uses-the-broadcast-channel');

[groovecoder]

Closing this. More refactoring/break-out can happen with follow-up issues.