All tests fail in Web Component Tester for Firefox - polymer

Question

After creating a clean copy of the Polymer Starter Kit, running the tests using the Web Component Tester ("test" Gulp task) results in all tests failing in Firefox.
The tests run through fine in both Chrome and IE.
The error is:
firefox 39 ✖ my-greeting-basic.html
Timed out loading http://localhost:2000/components/polymer-starter/my-greeting-basic.html?
<unknown> at done at /components/mocha/mocha.js:1846:0
<unknown> at Runner.prototype.run/< at /components/mocha/mocha.js:5213:0
<unknown> at EventEmitter.prototype.emit at /components/mocha/mocha.js:616:0
<unknown> at start/< at /components/mocha/mocha.js:5203:0
<unknown> at Runner.prototype.runSuite at /components/mocha/mocha.js:5103:0
<unknown> at start at /components/mocha/mocha.js:5201:0
<unknown> at Runner.prototype.run at /components/mocha/mocha.js:5226:0
<unknown> at Mocha.prototype.run at /components/mocha/mocha.js:1849:0
<unknown> at g at /bower_components/webcomponentsjs/webcomponents.min.js:11:0
<unknown> at w at /bower_components/webcomponentsjs/webcomponents.min.js:11:0
<unknown> at f at /bower_components/webcomponentsjs/webcomponents.min.js:11:0
<unknown> at p at /bower_components/webcomponentsjs/webcomponents.min.js:11:0
404 GET /components/polymer-starter/my-list-basic.html
firefox 39 ✖ my-list-basic.html
Timed out loading http://localhost:2000/components/polymer-starter/my-list-basic.html?
firefox 39 Tests failed: 2 failed tests
Test run ended in failure: 2 failed tests
Process terminated with code 1.
In the browser the calls to the test suites result in 404s.

Answer 1

The issue is that Firefox in Windows screws up when it sees backslashes in a path. Took me forever to figure it out, but I've opened a ticket on the relevant project and submitted a pull request for a fix I came up with.
If you're impatient you can navigate to <your project>/node_modules/web_component_tester/runner/webserver.js and put the following before line 80(options.webserver.webRunnerContent = INDEX_TEMPLATE(options))
options.suites = options.suites.map(function (cv) {
return cv.replace(/\\/g,'/');
})
This will change backslashes in the path to forward slashes which Firefox doesn't have a problem with.