solidity – How to Check Events in Truffle Tests

Seeing as there isn't a detailed updated answer:

As @pors mentioned, web3.js has a getPastEvents function. You can have it run at startup, using a syntax like:

myContract.getPastEvents('MyEvent');

The docs for this function are here. You can also filter by a specific topic, set a range of blocks to check, and more. Here's an expanded example, taken straight from the docs linked above:

myContract.getPastEvents('MyEvent', {
    filter: {myIndexedParam: [20,23], myOtherIndexedParam: '0x123456789...'}, // Using an array means OR: e.g. 20 or 23
    fromBlock: 0,
    toBlock: 'latest'
}, function(error, events){ console.log(events); })
.then(function(events){
    console.log(events) // same results as the optional callback above
});

This will not continue listening for events to the best of my knowledge. You could do this with events, however:

MyContract.events.MyEvent()

The function takes an object with parameters as an argument, much like getPastEvents(), see the docs here for more details. Based on the question, this would seem to be the best fit for the OP's particular use case.

(There is a similar function called allEvents for subscribing to all events from a particular contract - docs)

@pors also suggests using subscribe to get past events, and to continue to listen for new events. The docs are here. Note that you'll need to provide the topics you want to listen for. (Here's an explainer for event topics, you can get the topic for your event by hashing the event signature (eg Transfer(address,address,uint256) of the event with keccak256).

I've discovered that not all events are displayed in the truffle output window, although they might have fired correctly with the execution of a contract. I believe this to still be an issue

After spending hours on this today I have come up with a solution to test that specific events are fired.

Here's my example truffle javascript test:

it("should do something that fires SaleMade", function() {
    return myContract
        .stockShelf("beer", "wine", {from: sellerAccount})
        .then(() => myContract.sell("water", "bread", {from: sellerAccount}))
        .then(() => utils.assertEvent(myContract, { event: "SaleMade", logIndex: 1, args: { name: "bread" }}));
}

The above filters the fired events that match the filter object passed to the assertEvent utility function I have in utils.js in the same folder. At the top of my javascript test I have declared:

var utils = require("./utils.js");

A snippet of my utils.js class is as follows:

var _ = require("lodash");
var Promise = require("bluebird");

module.exports = {
    assertEvent: function(contract, filter) {
        return new Promise((resolve, reject) => {
            var event = contract[filter.event]();
            event.watch();
            event.get((error, logs) => {
                var log = _.filter(logs, filter);
                if (log) {
                    resolve(log);
                } else {
                    throw Error("Failed to find filtered event for " + filter.event);
                }
            });
            event.stopWatching();
        });
    }
}

This requires other npm packages that aren't included with truffle by default. By default truffle doesn't include npm packages. I setup npm and installed the required packages like this:

npm init
npm install bluebird --save
npm install lodash --save

EDIT: Using testrpc