I have contracts under `./test/helpers/contracts` which are not being compiled. Contracts under . `./contracts` folder are compiled ok. Is there any setting that I am missing? Using it within buidler Versions: `"buidler": "^0.2.8"` `"solidity-coverage": "^0.7.1"` _`buidler.config`_: ```javascript ... usePlugin('@nomiclabs/buidler-truffle5') usePlugin('solidity-coverage') module.exports = { defaultNetwork: 'buidlerevm', solc: { version: '0.5.15', optimizer: { enabled: true, runs: 200 } } } ```