How to manually create the instance of the contract in truffle - ethereum

Question

Say I have 2 contracts like this
A.sol
import './B.sol';
contract A {
event BCreated(address addressOfB);
function createB(){
B b = new B();
BCreated(b);
}
}
B.sol
contract B {
uint8 value = 5;
function getValue() constant returns(uint8){
return value;
}
}
I am trying to write the test cases for these contracts.
I can deploy the contract A using the migrations file and will
get the instance of it.
But I am not sure about how to get the instance of contract B,
after the contract is created using function createB()
Ok I can get the address of the contract B in events after calling function createB(),
But not sure about the instance.
For this example, you can say that I can separately test contract B as it doesn't do much.
But in the real case, I need to create an instance using the address coming from the event.
Here is the little bit of js code for truffle test file
In this I have the address of B
var A = artifacts.require("./A.sol");
contract('A', (accounts) => {
it("Value should be 5", async () => {
let instanceOfA = await A.deployed()
let resultTx = await instanceOfA.createB({ from: accounts[0] });
console.log("Address of B: " + resultTx.logs[0].args.addressOfB);
/**
* How do I create the instance of B now?
*/
})
})

Answer 1

You can try to do it like this
var A = artifacts.require("./A.sol");
var B = artifacts.require("./B.sol");
contract('A', (accounts) => {
it("Value should be 5", async () => {
let instanceOfA = await A.deployed()
let resultTx = await instanceOfA.createB({ from: accounts[0] });
console.log("Address of B: " + resultTx.logs[0].args.addressOfB);
let instanceOfB = await B.at(resultTx.logs[0].args.addressOfB);
})
})