How test game on low performance(mode)？

[Antypodish]

To avoid uneeccessery threads duplication, I will link to relevant thread

Games system requirements ?

You profile your game. You can estimate performance based on your experience. But for the most, you test on target audience hardware. Either you test yourself, on weakest or target device you are going to support. Or you run playtest with your testers, to find out what you can support.

See also other answers in the linked thread.