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I want to test whether my smart contract functions return the correct error messages

example function in solidity

function transform (uint256 input) public returns (uint256){
require (input>1, "the value has to be greater than 1"
}

However, when i try to test whether a value of 0 triggers the correct error message, my test fails.

expect(await contract.connect(addr1).transform(0)).to.throw("values smaller than 1 are not allowed");

The error I am receiving:

 1 passing (828ms)
  1 failing

  1) Minting of Tokens
       transform should throw the correct errors:
     Error: VM Exception while processing transaction: reverted with reason string 'values smaller than 1 are not allowed'
    at ProjectL.mintLottoSchein (contracts/tests.sol:104)
    at EdrProviderWrapper.request (node_modules\hardhat\src\internal\hardhat-network\provider\provider.ts:446:41)
    at HardhatEthersSigner.sendTransaction (node_modules\@nomicfoundation\hardhat-ethers\src\signers.ts:125:18)
    at send (node_modules\ethers\src.ts\contract\contract.ts:313:20)
    at Proxy.mintLottoSchein (node_modules\ethers\src.ts\contract\contract.ts:352:16)
    at Context.<anonymous> (test\test.js:42:14)

Could someone please help me out?

thx

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2
  • What’s the error that you’re getting?
    – SYED ASAD KAZMI
    Commented Jun 25 at 12:27
  • I added it to the original question
    – PupSt4r
    Commented Jun 25 at 12:36

1 Answer 1

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You need to use .to.be.revertedWith and the exact error string used in the require, like:

expect(await contract.connect(addr1).transform(0)).to.be.revertedWith("the value has to be greater than 1");

P.S., You have to install @nomicfoundation/hardhat-chai-matchers dependency, if it’s not installed already.

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3
  • Can you share the minimum reproducible code via GitHub, so that I can try debugging the same on my end?
    – SYED ASAD KAZMI
    Commented Jun 26 at 5:56
  • 1
    It works now. In your code example, the "await" keyword is at the beginning of the line. In my code, the "await" was inside the expect() function. I changed it accordingly and then received an error that led me to install @nomicfoundation/hardhat-chai-matchers. Now it works perfectly. thank you for your help!
    – PupSt4r
    Commented Jun 26 at 6:18
  • Great. Thanks for pointing out. I’ve edited the answer accordingly.
    – SYED ASAD KAZMI
    Commented Jun 26 at 6:38

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