Examples of event logging in web3.js. Take note that when used with testrpc/ganache, there are various bugs where events don't get fired or get fired twice. More here: https://github.com/trufflesuite/ganache-cli/issues/338. I also prefer using async/await instead of callbacks.

EventTest.js

pragma solidity ^0.4.18;

contract EventTest {

    event LogEventTest(uint _x);
    event LogOtherEventTest(address indexed _sender);

    function emitEvent(uint x) public {
        LogEventTest(x); 
    }

    function emitOtherEvent() public {
        LogOtherEventTest(msg.sender); 
    }

}

eventTest.js

var EventTest = artifacts.require("./EventTest.sol");

contract('EventTest', function(accounts) {

    let eventTest;
    let eventHandler;
    let otherEventHandler;

    // This gets run once in the beginning of the test. 
    // Typical practice in ICO tests is to have `beforeEach` instead of `before`
    // so that the contract is reinstantiated at the beginning of every test.
    before('Deploy contract', async function() {
        console.log('deploying...')
        eventTest = await EventTest.new()
    });

    // Calls the `emitEvent` function 3 times. We expect to see the events logged one by one in our terminal.
    it("will watch for events", async function() {
        // Initialize event that will monitor `LogEventTest` events from block 0 to the latest block
        eventHandler = eventTest.LogEventTest({fromBlock: 0, toBlock: 'latest'});

        // Starts watching asynchronously for `LogEventTest` events
        eventHandler.watch((error, log) => {
            // Do whatever you want
            if (!error) {
                console.log('Watched Log:', log.args);
            }
	  	  });
        await eventTest.emitEvent(42);
        await eventTest.emitEvent(31337);
        await eventTest.emitEvent(1337);
    	// Should stop watching (listening) for more events when you are done.
        // eventHandler.stopWatching();
    });

    // Get all past events from a specific event
    it('emits 2 other events and fetch them from blockchain history', async function() {
        await eventTest.emitOtherEvent();
        await eventTest.emitOtherEvent({from: accounts[1]});

        let otherEventHandler = eventTest.LogOtherEventTest({fromBlock: 0, toBlock: 'latest'});
        // Instead of watching, eventHandler.get will fetch all `LogOtherEventTest` logs 
        // from the smart contract and return them as a list.
        otherEventHandler.get((error, logs) => {
            console.log('Getting all `LogOtherEventTest` type events')
            if (!error) {
                logs.forEach(log => console.log(log.args))
            }
        });
    });

    it('gets all of the contract\'s events', async function() {
		let contractEvents = eventTest.allEvents({fromBlock: 0, toBlock: 'latest'});
        contractEvents.get((error, logs) => {
            console.log('Getting all contract  events')
            if (!error) {
                logs.forEach(log => console.log(log.args))
            }
        });
    });
});

Truffle Results

[~/eth_dev/EventHandling, 1, master+5, 35s]: truffle test
Using network 'development'.

Compiling ./contracts/EventTest.sol...


  Contract: EventTest
deploying...
Watched Log: { _x: BigNumber { s: 1, e: 1, c: [ 42 ] } }
Watched Log: { _x: BigNumber { s: 1, e: 1, c: [ 42 ] } }
    ✓ will watch for events (389ms)
Watched Log: { _x: BigNumber { s: 1, e: 4, c: [ 31337 ] } }
Watched Log: { _x: BigNumber { s: 1, e: 3, c: [ 1337 ] } }
    ✓ emits 2 other events and fetch them from blockchain history (259ms)
    ✓ gets all of the contract's events


  3 passing (904ms)

Getting all `LogOtherEventTest` type events
{ _sender: '0x2b716301dc5db5ad70e4ce673501b53812d16af3' }
Getting all contract  events
{ _x: BigNumber { s: 1, e: 1, c: [ 42 ] } }
{ _x: BigNumber { s: 1, e: 4, c: [ 31337 ] } }
{ _x: BigNumber { s: 1, e: 3, c: [ 1337 ] } }
{ _sender: '0x6a341d7835e4163deb192df32e249ad17743025d' }
{ _sender: '0x2b716301dc5db5ad70e4ce673501b53812d16af3' }

thx!