Truffle Testing – How to Access Deployed Contract’s Address in Truffle JS Tests

testingtruffletruffle-contract

I've written a test that involves returning the token balance that the contract itself holds. In the contract source file I would access the balance using the function getBalanceOf(this). However, when I include instance.getBalanceOf(this) in my JS tests, I get a new BigNumber() is not a number error.

I've narrowed it down to my tests not having access to the deployed contract's address. I know you can access it in Solidity tests using the DeployedAddresses.sol library, but is there any way to do it in JS tests?

Cheers,
Pryce

Best Answer

const contract = require('truffle-contract');
const TokenArtifact = require('./../../build/contracts/YourToken.json');

var Token = contract(TokenArtifact);
Token.setProvider(window.web3.currentProvider);
var tokenInstance = await Token.deployed();

Now,

tokenInstance.address

Will give you, your deployed contract's address.

Related Solutions

Truffle Contract Abstractions – How to Access from External JS Script

Not sure whether this is the intended way, but experimenting with bits and pieces of code found around the Internet resulted in something that seems to be working. Here's what I did in my javascript app:

....
const artifacts = require('../build/contracts/MyContract.json')
const contract = require('truffle-contract')
let MyContract = contract(artifacts);
MyContract.setProvider(web3.currentProvider);    
return MyContract.deployed().then(function(instance){      
  return instance.sendTransaction(param1, param2, {from: accounts[0]});
}).then(function(tx_id){
....

The json file is what was produced by truffle when migrating MyContract. Note that I had to install truffle-contract (on top of truffle) for this to work. If anyone has a more elegant way of doing this, please share!

Truffle Framework – How to Convert BigNumber to Number

If your token have 18 decimals

like an ether you can use

then(function(balance) {
    console.log(web3.fromWei(balance.toNumber(), "ether" ) );
})

Use fromWei to convert your bigNumber to ether and then convert it to Number. Be aware that unnecessary 0 after the floating point will not be displayed.

In web3 ^1.0 it may change to web3.utils.fromWei instead of web3.fromWei doc. Note that truffle ^5.0 uses web3 ^1.0.

If you have a different token decimal

Let's say 6. You'll have to do the conversion manually with something like:

var tokenBalance = balance.ToNumber() / Math.pow(10, tokenDecimals)