Testing Wagmi with a MockedProvider

[jasperverbeet]

Hi,

I use Wagmi for all my Ethereum(-like) projects, and I love the library.

However, one thing that isn't optimal in my opinion is testing my implementations. Currently, this repository itself is testing against an Anvil instance, but I prefer fully isolated (unit) tests without depending on external service for speed and reliability reasons. I couldn't find a way to do that...

That's why I created an alternative called MockEth, which provides a MockProvider for Ethers that intercepts and returns mocked data instead of performing the actual call.

Currently, it supports reading contract data and watching for events, but I'll be working on adding more features soon.

Here is an example:

// ethers.test.ts
import { Contract, BigNumber } from 'ethers'
import { MockedProvider } from '@byont/mocketh'
import { ExampleAbi } from './example-abi'

/** Mocking parameters */
const contractAddress = '0xbc4ca0eda7647a8ab7c2061c2e118a18a936f13d'
const balanceAddress = '0x31b0c4112a9aa5b79ca5883465bfc4cd013c6282'
const mockedBalance = BigNumber.from('999999999')

/** Create a new mock provider */
const mockProvider = new MockedProvider({ chainId: 1, name: 'mainnet' })

/** Mock the actual function */
mockProvider.mockContractFunction({
  abi: ExampleAbi,
  address: contractAddress,
  functionName: 'balanceOf',
  args: [balanceAddress],
  returnValue: [mockedBalance],
})

/** Execute the call how you would normally do it */
const contract = new Contract(contractAddress, ExampleAbi, mockProvider)
const [returnedBalance] = await contract.functions.balanceOf(balanceAddress)

/** Notice how the balanceOf function returns the mocked value */
expect(mockedBalance).toEqual(returnedBalance)

/** Clear all mocks so we leave a clean test */
mockProvider.clearMocks()

I've also included a Wagmi example here: https://github.com/Byont-Ventures/mocketh/tree/main/examples/1-wagmi.

It would be super cool if someone could check it out and let me know what you think!

Again, thanks for providing such an awesome library!

~ Jasper