I\'d like to reopen the question posed here and here about testing file uploading within Nightwatch.js which uses selenium.
Both links have the recommended solutio
In my case, I had an additional problem because the file I was trying to upload was too high up in my directory structure.
As soon as I moved the file to the same level (or in a subdirectory of) the actual test files, things worked.
From a script living in my page-objects folder:
// No dice:
var fullPath = require('path').resolve(__dirname + '/../../somefile.pdf');
// Works:
var fullPath = require('path').resolve(__dirname + '/../somefile.pdf');
this.setValue('input#fileUpload', fullPath);