It doesn't really matter; if you get a slow laptop you can run the graphics in software mode to test the correctness of your rendering, the only thing I can think you need a powerful laptop for is if you're trying to do performance measurements, at which point I wouldn't recommend using a laptop. As long as you can get at least 10 fps on a laptop you're probably fine as far as testing goes. Just make sure you have the ability to time step your game/simulation.

Regular time stepping uses delta from last frame to update, time stepping is using a value you set yourself as an update delta and only updating when you get a space bay down command or something.

Word of warning, before you buy a new laptop, find out what chipset it's using (mainboard) or graphics card, and google that for directX problems. If you get a laptop that has bad graphics drivers, using software rendering mode isn't going to help. For example I've got a 945gm chipset that doesn't do a specific draw mode in directX at all ( one of the less commonly used indexed primitives draw calls, some games would crash if I tried to play them on the laptop )

I recently bought an Alienware M17X. You can make it as good as you want.
I got an i7 with 8gb mem and a Geforce 580m with 2gb in it. It is really an awesome laptop and great for DX11 development even. It even runs BF3 perfectly smooth
Can highly recommend that one. I ordered it from the dell website. Very pricy though, but you can also keep it lower performance for cheaper. There are also other less advanced laptops from Alienware, which are a bit smaller, but I didn't like the keyboard layout of those, as that would suck a bit with programming.

Is battery life a problem?
As a side note, I have a laptop i3... I'm totally unsatisfied with battery life, although I have plenty of CPU power I don't use.
But of course, I suppose OP is looking for computer that can be carried around rather than a laptop.
Seriously, how to get decent battery life?

And seriously, stop the high-end madness for development. It's not like you're going to tax your system any time soon.

And seriously, stop the high-end madness for development. It's not like you're going to tax your system any time soon.

That very much depends on what you're working on.

I sometimes which these guys would design laptops which don't even have a battery, meaning more space for more powerful components - the only other place I might use the laptop is on a train and they have power sockets anyway.

those are called "DeskNotes", which are meant to be desktop replacement. I had one like 6-10 years ago (I guess), it had no battery, but instead a desktop-cpu (dual core P4) which got quite hot, but was ok', as there was enough space for enough cooling.
not sure if they're still on the marked, but it was quite a nice idea, they weren't more expensive than a PC (they had no battery), a tft display was integrated (back then a CRT was more common on a desktop) and the company where I bought it, used desknote barebones, it allowed you to configure all parts just like on a desktop PC.





if you don't care bout battery life, whether they're heavy or big (compared to e.g. an MacBook Air), get an alienware notebook.

I need a laptop myself, and I'd buy an Alienware m14x tomorrow if it didn't look like a toy for adolescents. I need to take this thing to conferences, etc.

+1
dell XPS are kind of similar, usually they have less GPU power, but that's probably because you don't want to hear a noisy fan (while you might not care that much during playing).


( sadly the smallest ones you can buy are Dell XPS 14z and XPS 14R, but on the other side, you can choose between with intel, ATI and NVidia GPUs.)