Hi there, I would really like to find a computer game that resembled as much as possible warhammer fantasy. It would be great for testing new lists and crazy ideas before buying the miniatures or before playing with friends. It would be much quicker to play a turn based online game like that, and it would allow to improve playing skills dramatically. Does such a game already exist?
Sadly, I don't think anything like that has ever been made (more's the pity). The best you'll get for getting the experience of playing tabletop warhammer on your computer is the Warhammer:"inset title here" games that ran from the 90s to the late 00s. If you like classic games that favour strategy over graphics, I can recommend Warhammer: Dark Omens. They're nothing like as expansive as you've described though - and you certainly couldn't use them to try out lists etc.
I would recommend www.universalbattle.com It's a website that allows you to play games of warhammer quite easily and has all of the appropriate tools. It's well designed and pretty cheap for a membership which would allow you to design or own armies and models. As for an actually video game, supposedly Total War: Warhammer should be announced soon and be coming out either in the final quarter of this year or early next year if my memory is serving me correctly.
Should be out by the end of this year. I imagine whatever next big gaming event happens will report it.