How can I do CPU mining on testnet?

Question

I'm trying to do cpu mining on testnet to debug coinbase transactions in my application.

Tried running GUI miner, I get the below output:

2014-07-31 11:31:51: Running command: poclbm.exe testnetuser:test123456@localhost:18332 --device=0 --platform=0 --verbose -r1
2014-07-31 11:31:51: Listener for "Default" started
2014-07-31 11:31:53: Listener for "Default": No PyOpenCL
2014-07-31 11:31:53: Listener for "Default": Not using OpenCL
2014-07-31 11:31:53: Listener for "Default": Nothing to mine on, exiting

I tried UFASoft miner, set the listening port to 18332 but nothing happens.

What is the easiest way to do cpu mining on testnet?

Is there another way of getting coinbase transactions in my testnet wallet?

Answer 1

Even on testnet the difficulty is sufficiently high that it will take you a long time to mine anything using cpu. (Lots of people testing ASICs, presumably.)

Your best bet is probably Testnet in a box. Then you can cpu mine just by using ´setgenerate true´ in Bitcoin Core.

Answer 2

Testnet has a special rule, which makes it easy to mine in particular circumstances. If there are no blocks found for more than 20 minutes, the difficulty drops and you can easily mine a testnet block with a normal CPU. Obviously your luck depends on if other powerful miners are mining or not, so sometimes you will find more blocks in a week, sometimes no block for months.

Heck, you can even mine with bitcoin-cli:

while [ 1 ]
do
    bitcoin-cli generatetoaddress 1 "2N5fJkfCv4cF6vsa5QQJnsazBKWNXynn9zp" 10000000
done

For example, I found 6 blocks in less than 2.5 months, but your luck depends on the activity of other miners.