[Ethereum] How to test events that were sent by inner transaction / delegate call

openzeppelin-contractssoliditytestingtruffletruffle-test

Usually, using truffle I can check for events like this:

    let { logs } = await myContract.doSomethingImportant( xxx );

    // 1500 tokens are expected to get
    expectEvent.inLogs(logs, 'myImportantEvent', {
      arg1: 111,
      arg2: 'and so on'
    });

However, logs contains only the events that was fired directly inside of the contract function withdrawVestedTokensByTimestamp:

function doSomethingImportant(uint256 x) public returns(uint256) {
    // ... do something else here ...

    emit myImportantEvent(x, amount);

    return amount;
}

However, if in this function a token transfer will happen or another function is called, which would fire events itself, they don't appear in the logs.

Running tests with truffle test --show-events will list all of the expected events, but how can I catch them inside truffle test?

Best Answer

Use openzeppelin-test-helpers

Specifically use expectEvent.inTransaction

I created an example in the community forum for how to use: https://forum.zeppelin.solutions/t/how-to-check-for-events-that-was-dispatched-in-a-nested-operation/955/2

Related Solutions

Truffle Testing – Logs Not Showing Emitted Events in JavaScript

Turns out transaction receipt logs only include events emitted in the context of the direct contract function being called. If the called function makes another call to a separate external contract that emits an event, those won't be included even if there are emitted.

To make use of those emitted events from other contracts:

const sha3 = require('js-sha3').keccak_256
...

const tx = await instance.someFunction(();
let event = tx.receipt.logs.some(l => { return l.topics[0] == '0x' + sha3("Stored()") });
assert.ok(event, "Stored event not emitted");

where someFunction is a function that calls a function of another contract different to instance.

This grabs the logs from the receipt object. The logs should contain topics, the first of which is a hashed event signature. Thus we can use what we expect our event signature to be, hash it and test for existence in the logs. This works because all events are included in receipt logs but are not returned in the transaction logs provided by truffle/ganache.

This post helped.

On later versions of Truffle (have tested with v5.1.0), the same logs and topics are found under a different transaction receipt property rawLogs:

const tx = await instance.someFunction(();
let event = tx.receipt.rawLogs.some(l => { return l.topics[0] == '0x' + sha3("Stored()") });
assert.ok(event, "Stored event not emitted");

Best Answer

Related Solutions

Truffle Testing – Logs Not Showing Emitted Events in JavaScript

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