  Smart contracts are immutable, verifiable, and autonomous pieces of code that
can be deployed and ran on blockchain networks like Ethereum. Due to the
immutability nature of blockchain, no change is possible on a deployed smart
contract or a verified transaction. On the other hand, there are millions of
dollars carried by smart contracts in Ethereum blockchain, and hence, a faulty
smart contract can lead to a huge monetary loss. Therefore, it is important for
smart contract developers to fully test and check the correctness of their code
before deploying it on the blockchain. In this paper, we propose a testing
mechanism for smart contracts in Solidity language, based on mutation testing.
We analyzed a comprehensive list of known bugs in Solidity smart contracts, and
designed 10 classes of mutation operators inspired by the real faults. Our
experimental results show that our proposed mutation operators can regenerate
10 of 15 famous faulty smart contracts, which have resulted in millions of
dollars loss. The results show the effectiveness of our proposed mutation
operators in detecting real faults in Solidity smart contracts. We have also
extended {\em Universal Mutator } tool with our mutation operators, so that it
can automatically generate mutants for smart contracts written in Solidity.
