test process：
- install yarn
- switch node version >= 14
- cd flex-saving
- yarn install
- start local ganachi (default port and params)
- change .ganache/accounts with ganachi generated private keys
- install native solc and change solc command with saddle-config if you need compile contracts(for now there is already an available contracts.json in .build)
- npx saddle compile
- npx saddle test