OpenZeppelin test helper: expectEvent.inTransaction error

Question

I'm trying to use OZ Test helpers to pass a test when a specific event is emitted. Here is the logic:

• I call function1 with a JS Promise.
• function1 calls function2 which emits an event.

Parts of code have been omitted for readability:

test.js

const { expectEvent } = require('@openzeppelin/test-helpers');
const { ethers }      = require("hardhat");

describe("test", function() => {
let mycontract;

before( async() => {
    const Mycontract = await ethers.getContractFactory("MyContract");
    mycontract = await Mycontract.deploy();
})

it("expected event is emitted.", async() => {

    const{ hash } = await mycontract.function1();

    await expectEvent.inTransaction(hash, mycontract, "THIS_EVENT",
     {message:"This event has happened."} );
 });
});

myContract.sol

pragma solidity ^0.6.0;

contract MyContract
{
string message;

constructor(){
 _message = "This event has happened."
}

event THIS_EVENT(string message);

function1() {
 function2();
}

function2() {
 emit THIS_EVENT("_message")
 }

}

Error message:

     Error: Unknown contract object

How can I write a test to pass when a specific event is emitted as a result of a nested function call ?

Your time is much appreciated,
Edit hardhat: 2.2.1 test-helpers: 0.1.4

Answer 1

Try this

it('expected event is emitted', async function() {
    const receipt = await this.mycontract.function1();
    expectEvent(receipt, 'THIS_EVENT', {
        message: 'This event has happened.',
    });
});