Is there a way to set gas fees to 0 for unit tests in ethers js?

Question

All the contract deploying and setup cost some gas fees.

Is there a way to disable or set gas fees to 0, so we can calculate and test only the meaningful business logic change on the balance, without minding the little changes of payed gas fees ? I'm using hardhat.

Answer 1

In your hardhat.config.js, you can explicitly state the network that you are using and subsequently the gasPrice that you would like to use. In the docs, there is a gasPrice configuration which can be set.

gas: Its value should be "auto" or a number. If a number is used, it will be the gas limit used by default in every transaction. If "auto" is used, the gas limit will be automatically estimated. Default value: "auto".

Alternatively, if you're hung up on gas, you can also the plugin hardhat-gas-reporter which can be read more on here.

Answer 2

If you want to optimize your function's gas cost, with hardhat it's very easy and costs nothing.

Write a unit test for each business logic function (as you probably already have), now you can measure gas costs in several possible ways -

• Install and run Ganache, then run your tests npx hardhat test --network ganache, in Ganache you'll be able to see how much gas each method consumed.
• Integrate hardhat-gas-trackdooor package, it'll print gas cost for each test:
• Use hardhat-gas-reporter, it'll print a report at the end of gas cost per function.