What happened to Bitcoin testnet? Confirmation time is very short.
10 confirmation occurred in three minutes.
I use Bitcoin core v0.16.0 (64-bits)
The Bitcoin testnet has a very low difficulty. Usually there are few people who mine on testnet. However, occasionally there will be enough people mining on the testnet for the difficulty to increase. But when those people go away, the difficulty is too high for the remaining testnet miners.
To combat this, there is a special rule that resets the difficulty to 1 in order to keep the testnet running. Unfortunately the way that this rule works allows large miners to game it so that the difficulty is constantly low.
What we are currently seeing on the testnet is exactly that. Someone with a lot of hashrate is mining on the testnet and gaming the difficulty to be very low. This means that blocks will be found very quickly until this person stops mining on testnet.
Nothing is wrong with the testnet, and there is nothing wrong with your node or the Bitcoin Core software.