On the topic of running behat tests on Windows 8.1 I use a linux VM on my home PC (i5 ivy bridge desktop version - 8Gb - SSD).
I installed a Moodle dev environment on Linux Mint with this script:
https://github.com/mouneyrac/mooduntu/blob/master/mooduntu.sh
Then I installed samba so I can use PHPStorm in Windows and make fast searches. I mean "fast" in the world of remote access of course - about 6 seconds for scanning all "get_string" in Moodle - but you can use git grep in the PHPStorm terminal anyway:
https://github.com/mouneyrac/mooduntu/blob/v1.0/mooduntu.sh#L20-L40 - it's an old version of the script with samba instruction, I removed the instruction from the last version.
Then I added a NAT network (for internet) + a host-only network with static IP so it never changes - you need to set the host-only network up in virtualbox and in linux - You need to google it, it's not obvious. I don't remember the exact steps.
Then I use "mdk behat" (https://github.com/FMCorz/mdk) to setup behat in the VM. Running a behat test inside the VM is surprisingly not that slow - I won't run the full test suite thought.
That's the best compromise I found for having all development features of a native linux without losing too much speed.