How to make a swamp biome?

I know this has been asked before but none of the answers really work, Ive seen in another post that someone responded and they said just set something in the code of the biome from DEFAULT to SWAMP and that doesn't really do anything at all, the only thing it does it make little patchs of water and grass sometimes BUT  they are only like 10 blocks long and just are rare so it just looks like a normal biome, id even do something requiring coding to be able to make a swamp biome, so is there any solution?, and possibly test to see if it works before you post it here.