Testing blockchain forks I want to test if a service can manage a blockchain fork. However there is no way to get bitcoind to create test forks under the regtest mode. I've tried modifying it to generate blocks with arbitrary prevblock hashes but it is not easy due to the high code complexity. I've managed to get it to create forks on-top of earlier blocks, however, I can't get it to generate blocks for conflicting transactions (double-spends and malleability changes), largely due to all of the "pruning" code. Surely someone has already come up with a solution, as this is a vital thing to test? I can't find anything on-line to help with testing fork scenarios.

I'm thinking that perhaps I should have used another technique? That I should have run 3 bitcoind regtest nodes and isolate them so that I can create multiple blockchains. 2 of them generate competing chains, and the other interfaces with the application. I can generate a fork scenario with the first two nodes, sync one of the nodes to the 3rd node and then sync the other node to generate the fork? I'd need to use a combination of addnode and tcpkill (?) to sync and then re-isolate the nodes. 

This seems a ridiculous thing to do to test something so simple, so is there a better way?
You can use the invalidateblock RPC commands to create blockchain forks.

invalidateblock hash tells a node to consider hash invalid, so just generate a bunch of blocks, invalidate one somewhere down the chain on one of the regtest nodes, and have that node generate a bunch more to create a fork.

See qa/rpc-tests/mempool_resurrect_test.py in the Bitcoin Core tree for a python example.