Buidler comes built-in with Buidler EVM, a development network to deploy
and run your contracts on, facilitating testing and debugging. Buidler EVM is
just like Remix and Ganache, so you don't have to worry about consensus bugs.
By default, an instance of Buidler EVM will be automatically created when your run a task, script or test your smart contracts. You don't need to do anything to enable it.
Solidity stack traces
Buidler EVM has first-class Solidity support. It always knows which smart contracts are being run, what they do exactly and why they fail.
This is an example of a Buidler EVM exception:
Error: Transaction reverted: function selector was not recognized and there's no fallback function at ERC721Mock.<unrecognized-selector> (contracts/mocks/ERC721Mock.sol:9) at ERC721Mock._checkOnERC721Received (contracts/token/ERC721/ERC721.sol:334) at ERC721Mock._safeTransferFrom (contracts/token/ERC721/ERC721.sol:196) at ERC721Mock.safeTransferFrom (contracts/token/ERC721/ERC721.sol:179) at ERC721Mock.safeTransferFrom (contracts/token/ERC721/ERC721.sol:162) at TruffleContract.safeTransferFrom (node_modules/@nomiclabs/truffle-contract/lib/execute.js:157:24) at Context.<anonymous> (test/token/ERC721/ERC721.behavior.js:321:26)
Automatic error messages
Buidler EVM always knows why your transaction or call failed, and uses this information to make debugging your contracts easier.
When a transaction fails without a reason, Buidler EVM will create a clear error message in the following cases:
Calling a non-payable function with ETH
Sending ETH to a contract without a payable fallback function
Calling a non-existent function when there's no fallback function
Calling a function with incorrect parameters
Calling an external function that doesn't return the right amount of data
Calling an external function on a non-contract account
Failing to execute an external call because of its parameters (e.g. trying to send too much ETH)
Calling a library without
Incorrectly calling a precompiled contract
Supported Solidity versions
Buidler EVM can run any smart contract, but it only understands Solidity 0.5.1 and newer.
If you are compiling with an older version of Solidity, or using another language, you can use Buidler EVM, but Solidity stack traces won't be generated.
Solidity optimizer support
Buidler EVM can work with smart contracts compiled with optimizations, but this may lead to your stack traces' line numbers being a little off.
We recommend compiling without optimizations when testing and debugging your contracts.