Lesson 14: Few questions in unit-testing RandomIpfsNFT

[ManuWeb3]

Hi all,

1). How do we unit test the revert clause in the withdraw() function below in RandomIpfsNft.sol ?

function withdraw() public onlyOwner {
        uint256 amount = address(this).balance;
        (bool success, ) = payable(msg.sender).call{value: amount}("");
        // this does not do any exception handling / throwing upon failing, just returns bool
        if(!success) {
            revert RandomIpfsNft__TransferFailed();
        }

I checked the unit tests of FundMe.sol and Raffle.sol git repos for the same revert but found that it wasn't tested there either.

Any way we can do it ?

2). What is the need to check assert.equal(tokenUri.toString().includes("ipfs://"), true) in fulfillRandomWords() unit test when we've aready tested assert(dogTokenUriZero.includes("ipfs://")) in the Constructor unit test ?

fulfillRandomWords() unit test:

describe("fulfillRandomWords", () => {
              it("mints NFT after random number is returned", async function () {
                  await new Promise(async (resolve, reject) => {
                      randomIpfsNft.once("NftMinted", async () => {
                          try {
                              const tokenUri = await randomIpfsNft.tokenURI("0")
                              const tokenCounter = await randomIpfsNft.getTokenCounter()
                              assert.equal(tokenUri.toString().includes("ipfs://"), true)
                              assert.equal(tokenCounter.toString(), "1")
                              resolve()
                          } catch (e) {
                              console.log(e)
                              reject(e)
                          }
                      })

Constructor unit test:

describe("constructor", () => {
              it("sets starting values correctly", async function () {
                  const dogTokenUriZero = await randomIpfsNft.getDogTokenUris(0)
                  const isInitialized = await randomIpfsNft.getInitialized()
                  assert(dogTokenUriZero.includes("ipfs://"))
                  assert.equal(isInitialized, true)
              })
          })

Aren't both tokenURI("0") & getDogTokenUris(0) eventually checking the same thing, which is, whether our string array of s_dogTokenUris[index] got correctly initialized with all the 3 IPFS URIs ?

[RoboCrypter]

@ManuWeb3 :

Yes, we can test our withdraw function as well.

And, about your second question : So, tokenURI and getDogTokenUris both will give the same results.

And its upto you, If you wanna test it once or twice, Its totally fine to only test it once!

In our constructor we just checked, If the constructor is initialized correctly or not!

And In our fulfillRandomWords test we checked it to see, The Nft is minted or not by checking the tokenURI at 0!

[ManuWeb3]

Hey @abossofmyself ... thanks for taking out your time.

1). Actually, I wasn't able to figure out how will withdraw( ) fail and revert but @krakxn answered that.

2). Noted!!

[RoboCrypter]

@ManuWeb3 : You can test that revert statement error by withdrawing with the Not Owner address!

That should resolve your Question : 1

And I totally forgot about your Question : 1 when I was answering your discussion!

Hopefully, This will help!

[ManuWeb3]

Hey... no worries...

I did already test the modifier onlyOwner by trying to withdraw() with Non-owner address and yes, it reverted and passed.

But, I am wondering, how can we make .call() fail here.

Like, how can we artificially supply lesser gas to revert it in a test?
OR any other scenario where it reverts ?

Just tried with zero amount but it sent zero amount and did not revert.

[RoboCrypter]

@ManuWeb3 : To get the .call to fail you need to try and send the funds to a contract that doesn't have a receive() or fallback() function.

[ManuWeb3]

Thanks for this tip. I'm trying it.

[krakxn]

1. Insufficient gas/amount or a fallback which leads to a revert.

2. I will answer this later (leave a reply though, so as to notify me).

[ManuWeb3]

Hey @krakxn ..

1). Thanks for this info. I'll try.

2). You can ignore this as @abossofmyself answered that. However, just in case, you want to add something to it.

[ManuWeb3]

Hey...

1). Just tried to revert with insufficient amount but it did not as value: zero also kind of gets executed by .call().

I mean I ran requestNft() without passing any amount in value and withdraw() still went through.

So, the below test failed.

await expect(randomIpfsNft.withdraw()).to.be.reverted;

How can we write the test with insufficient gas or fallback ?

[krakxn]

A conditional in the contract w/ a custom error when the transfer fails, then a test in your script w/ revertedWithCustomError

2: For me to answer this, is it the same contract? (or just paste the entire unit test and the contract here)