Mocha.opts not working as expected with client config

[nickytonline]

Hi, I'm just wondering about mocha.opts. I know it is now supported via

{
   ...
   client: {
      mocha: {
         opts: './path-to-mocha-opts'
      }
   }
...
}

Here's the setup we have:

mocha.opts file contents:

--require babel-core/register
src/**/*.spec.js

here's the karma.conf file:

module.exports = function(config) {
  'use strict';
  config.set({

    basePath: '',
    port: 9880,
    colors: true,
    autoWatch: true,
    singleRun: true,
    browserDisconnectTimeout: 15000,
    browserNoActivityTimeout: 15000,

    // level of logging
    // possible values: config.LOG_DISABLE || config.LOG_ERROR ||
    //   config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
    logLevel: config.LOG_INFO,

    browsers: ['PhantomJS']
  });
};

and we extend it in gulp like so:

{
  configFile: __dirname + '/../karma.conf.js',
  frameworks: ['mocha', 'sinon-chai'],
  client: {
    useIframe: true,
    mocha: {
      opts: __dirname + '/../mocha.opts'
    }
  },
  singleRun: !isWatchmode
}

and here's our console output:

20 04 2017 13:57:39.644:WARN [watcher]: Pattern "babel-core/register" does not match any file.
20 04 2017 13:57:39.697:WARN [karma]: No captured browser, open http://localhost:9880/
20 04 2017 13:57:39.710:WARN [karma]: Port 9880 in use
20 04 2017 13:57:39.711:WARN [karma]: Port 9881 in use

With this configuration I am able to load the mocha.opts file, but when it gets parsed, it thinks that the require option is the file glob instead of it being the babel compiler. I know the configuration is correct because when I run node_module/.bin/mocha --opts ./path-to-mocha-opts, it runs fine.

Is there something different I should be doing in the config or my mocha.opts file?

[NullVoxPopuli]

I'd also love an answer to this.