Testnet will likely fork to BIP101

[YarkoL]

Why aren't there multiple testnets? It seems like a strange idea to only be able to run one experiment at a time. I can appreciate it still requires miners and nodes but I would've expected they'd allocate resources to different concepts.

They are (or actually, he is - for time being), see jtoomins post on Reddit
https://www.reddit.com/r/Bitcoin/comments/3s0uii/bip_101_has_activated_on_the_testnet_need_your/cwtkyka

[alani123]

Why aren't there multiple testnets? It seems like a strange idea to only be able to run one experiment at a time. I can appreciate it still requires miners and nodes but I would've expected they'd allocate resources to different concepts.

They are, see jtoomins post on Reddit
https://www.reddit.com/r/Bitcoin/comments/3s0uii/bip_101_has_activated_on_the_testnet_need_your/cwtkyka

This fork seems to be taking place on the one existing testnet, I think the last sentence in that post is nothing more that a hypothesis.

[worhiper_-_]

http://xtnodes.com/#testnet now shows blocks in the fork that highlights blocks that are larger than the previous block size cap 1 Mb.

[YarkoL]

This fork seems to be taking place on the one existing testnet, I think the last sentence in that post is nothing more that a hypothesis.

Because if you're going to test forking in somewhat realistic
scenario, you can only do it on "official" testnet. Performance on the other hand can
be tried out on a private testnet.

[spin]

Please note that this doesn't mean you need to run a BIP101 node to use the testnet.  Regular nodes will work fine and will just ignore the non-bitcoin blocks.

Why aren't there multiple testnets? It seems like a strange idea to only be able to run one experiment at a time. I can appreciate it still requires miners and nodes but I would've expected they'd allocate resources to different concepts.

Good question. I assume it's mostly due to lack of interest. In order to be able to test things on a network replicating bitcoin's one this network would need to have a decent number of participants. Starting an entirely new testnet out of the blue to test something temporarily likely wouldn't attract a decent amount of participants willing to put effort and resources into building it and maintaining for the tests. So the existing test net was used.

There is functionality to run your own private simulated testnet.  To test things out.