To better test and demonstrate several critical new features in the mainnet, we will upgrade Testnet 2.4 and launch Testnet 2.5. Testnet 2.5 will further improve the security and flexibility of the network.
Read more: https://medium.com/quarkchain-official/quarkchain-announces-official-launch-of-testnet-2-5-the-last-round-of-testnet-before-mainnet-43d47295ba1e