Background prevent istanbul to perform

[samudurand]

I wrote a karma configuration using Istanbul coverage that was working perfectly fine when I run it using Grunt, until I tried to make it run in background.

Here is the Grunt task :

karma: {
      unit: {
        configFile: 'karma.conf.js'
      },
      continuous: {
        configFile: 'karma.conf.js',
        singleRun: true,
        background: true
      }
    }

The tests are running well with or without the 'background' config, but if I let the 'background' then istanbul does not write the report (no error shown, just nothing generated).