Running behat tests in parallel (in two browser windows) - symfony

Question

I followed this blog as an example and read the ParallerRunner info. When I call bin/behat command, one browser window opens and runs all the tests successfully with the setting below.
symfony/behat.yml
default:
context:
class: Site\CommonBundle\Features\Context\FeatureContext
extensions:
Behat\Symfony2Extension\Extension:
mink_driver: true
kernel:
env: test
debug: true
Behat\MinkExtension\Extension:
base_url: 'http://symfony.local/app_test.php/'
javascript_session: selenium2
browser_name: firefox
goutte: ~
selenium2: ~
paths:
features: %behat.paths.base%/src
bootstrap: %behat.paths.features%/Context
I modified the behay.yml (as shown below) to run some tests in one browser window and some in another window, however it doesn't do that. What it does is, it opens two browser windows but they both run same tests! How can I overcome this issue?
symfony/behat.yml
default:
context:
class: Site\CommonBundle\Features\Context\FeatureContext
parameters:
output_path: %behat.paths.base%/build/behat/output/
screen_shot_path: %behat.paths.base%/build/behat/screenshot/
extensions:
Behat\Symfony2Extension\Extension:
mink_driver: true
kernel:
env: test
debug: true
Behat\MinkExtension\Extension:
base_url: 'http://symfony.local/app_test.php/'
files_path: %behat.paths.base%/build/dummy/
javascript_session: selenium2
browser_name: firefox
goutte: ~
selenium2: ~
shvetsgroup\ParallelRunner\Extension:
process_count: 2
paths:
features: %behat.paths.base%/src
bootstrap: %behat.paths.features%/Context
F1:
filters:
tags: "#backend"
F2:
filters:
tags: "#frontend"
BEHAT TESTS:
This should run in one window:
#frontend
Feature: User Login
#javascript
Scenario: I can login to the system
Given I am on "/login"
And I login as "user"
This should run in another window:
#backend
Feature: Admin Login
#javascript
Scenario: I can login to the system
Given I am on "/login"
And I login as "admin"

Answer 1

I setup parallel test execution with GNU Parallel and xargs.
Also implement consolidated report for all executed features.
Details in my article here:
http://parallelandvisualtestingwithbehat.blogspot.com/p/blog-page.html

Answer 2

find ./features -name "*.feature" |
parallel --gnu --halt-on-error=0 -j 3 --keep-order vendor/bin/behat -c src/my_directory/behat.yml
--halt-on-error possibilities are :
0 Do not halt if a job fails. Exit status will be the number of jobs
failed. This is the default.
1 Do not start new jobs if a job fails, but complete the running
jobs including cleanup. The exit status will be the exit status from
the last failing job.
2 Kill off all jobs immediately and exit without cleanup. The exit
status will be the exit status from the failing job.
-j 3 : Run 3 jobs in parallel
It work perfectly with selenium.