Cross-chain bridge contract allows to transfer ERC20 token from one chain to another, by burning amount on first and minting them on another. Also bridges have to have backend as Validator who catch events from bridges and sign hashes for redeem. ERC20.sol file need for tests*
Etherscan ChainBridge - https://rinkeby.etherscan.io/address/0x992A58374550483C6dA7Bfe67764fC7D8Afd3a17#code
Bscscan ChainBridge - https://testnet.bscscan.com/address/0x09801CF826d876E6cc2aa32f6127b099C8D0EA2C#code
Etherscan ExampleToken - https://rinkeby.etherscan.io/address/0x58Dea97d56BAF80aFec00B48A2FC158E7703Fe80#code
Bscscan ExampleToken - https://testnet.bscscan.com/address/0x125281199964620d35d63886F492b79415926661#code