Truffle test error: Cannot create instance of Vault; no code at address

Question

I'm trying to make a simple test in Truffle using Ganache where I call a function from a smart contract instance. This component will create a Vault and return me its address.

My truffle test does the following:

const VaultFactory = artifacts.require("./VaultFactory");
const Vault = artifacts.require("./Vault");

contract('VaultFactory', async () => {
    it("Should create a new Vault", async () => {
        let VaultFactoryInstance = await VaultFactory.deploy();
        let VaultAddress = await VaultFactoryInstance.CreateVaultContract.call();
        let VaultInstance = await Vault.at(VaultAddress);
    });
});

The VaultFactory.sol code that creates the Vault does the following (the Vault's constructor is empty):

function CreateVaultContract ()
    public
    returns(address)
{
    Vault newVault = new Vault();
    emit VaultCreation(msg.sender, newVault, VaultState.Created);
    return address(newVault);
}

The VaultAdress that I get is not empty, however, when I try to get the VaultInstance, it gives me the following error:

Uncaught Error: Cannot create instance of Vault; no code at address 0xed41bb9a56dad9b9d0901400f0a8de72d3cf1854

I tried doing a web3.eth.getCode(VaultAddress); to see if I had any code, but it returns me 0x0.

So, my VaultFactory contract seems to be deployed and looks like it created a Vault. But for some reason, I can't manage to get its instance. Any idea why?

Answer 1

let VaultAddress = await VaultFactoryInstance.CreateVaultContract.call();

should be:

let VaultAddress = await VaultFactoryInstance.CreateVaultContract();

Answer 2

I finally managed to get a working solution (even though I'm not sure it's the best one).

const VaultFactory = artifacts.require("./VaultFactory");
const Vault = artifacts.require("./Vault");

contract('VaultFactory', async () => {
    it("Should create a new Vault", async () => {
        let VaultFactoryInstance = await VaultFactory.deploy();
        let VaultReceipt = await VaultFactoryInstance.CreateVaultContract();

        //This returns the address of the newly created Vault
        let VaultAddress = VaultReceipt.logs[0].address;

        let VaultInstance = await Vault.at(VaultAddress);
    });
});

This way, I can get my Vault address and can get the instance of it. I then tried to call a function and it works perfectly!

Answer 3

I had two problems

Using .call() does not persist data

Factory factory = await Factory.deployed()
factory.createChild.call()

This doesn't work, because call will return the code that would run on-chain, but it won't actually save anything on-chain. It's like you never called the function at all.

Dynamic arrays don't need initialization

constructor() {
   children = new Child[](1)
}

Don't do this. If you do, it will init 1 element as null.
If you then call factory.children.call(0) that element will be 0x00000...
Obviously, there won't be any code at null.

Working

Solidity

contract Factory {
  event CreatedChild(address child);
  Child[] public children;

  function createChild() {
    Child child = new Child();
    children.push(child);
    emit CreatedChild(address(child);
  }
}

contract Child {}

Truffle

 it("should deploy child", async () => {
  const factory = await Factory.deployed();
  const tx = await factory.createChild();

  const childAddress = tx.logs[0].address;
  const firstChild = await factory.children.call(0);

  // console.log("tx return", childAddress);
  // console.log("array call", firstChild);

  assert.ok(childAddress !== 0);
  assert.equal(childAddress, firstChild);
});