Automated Testing for League of Legends

https://engineering.riotgames.com/news/automated-testing-league-legends

by jsnell • 10 years ago

246 74 10 years ago

engineering.riotgames.com

amenod• 10 years ago

Nice writeup! Sounds pretty similar to the way serious web apps are being tested (using Selenium & co.). I find it interesting that they built their own testing system though - couldn't they have used some existing framework?

badloginagain6• 10 years ago

A third party solution would be as hard, or harder, than developing an in-house solution. The challenge is setting up the interactions between all gameplay elements- it's going to very unique to each game.

The amount you'd need to abstract to make it reusable for other developers would make it nearly useless.

kyberias• 10 years ago

Are these all the automated test they run? The article doesn't seem to mention unit tests for example. Do they write and run unit tests? The test class example seems to assert a bunch of stuff that might be easier (and cleaner) to test in a set of unit tests.

Update: In particular this is weird:

"Tests make use of remote procedure call (RPC) endpoints exposed on the client and the server in order to issue commands and monitor game state. For the most part, tests consist of a fairly linear set of instructions and queries—existing tests cover everything from champion abilities to vision rules to the expected rewards for a minion kill. "

They test "rules for expected rewards" with an out-of-process python test program that connects to the client and server via RPC. Seems unnecessary complex way to test specific game rules.

Is this a symptom of a separate QA team and no developer-written unit-tests?

crdoconnor• 10 years ago

It's a more loosely coupled way to test than unit tests. That has certain advantages.

chipsy• 10 years ago

No, it's because game engines don't unit test well. There is too much I/O, latency dependent behavior, and shared mutable state to make it feasible outside of some math and low level format or protocol tests. Many game bugs are purely data bugs and result from a misconfiguration or a malformed asset. Manual testing of the result, following a checklist and creatively hammering on the system, is thus the default method.

What Riot is using is a form of integration test where manual user input is emulated to produce a result data set. What you aren't seeing in the test code is "everything else" that was needed to set up a running game state. This technique makes it easy for QA to jump in and see what's happening visually when a failure occurs, eliminating the need to slave away at a checklist.

badloginagain6• 10 years ago

It's useful as a framework for testing all game interactions. When you think about the amount of unique abilities for the hundred(?) unique characters and how they interact against eachother, the test matrix that results is massive.

Additionally, you want to use production server/client code as much has possible, while getting through the tests as quickly as possible (skip front end flow, matchmaking, etc.).

Using client/server endpoint calls are great because it allows these integration tests to be a list of instructions (the same instructions used by production code) to create a very deep test suite.

Integration testing is critical for games, where you have so many independent units interacting and changing each other's states.

developer23• 10 years ago

> When you think about the amount of unique abilities for the hundred(?) unique characters and how they interact against eachother, the test matrix that results is massive.

Definitely. They're at 130 champions right now. Each with four spell cast abilities, as well as a passive ability, and unique auto attack mechanics on some of them. There are indeed many interactions with specific abilities between champions. Add in interaction with the map and terrain itself, like unit collision and NPC minions and monsters. Then deal with the 154 items (the current count on the main map) players can add to their champion, many of which also interact with abilities, and some of which introduce additional abilities.

It must be both a nightmare and yet very interesting to handle creating a new champion for the game. Once they get past the step of even deciding how the new champion's abilities should interact with other champions, they then need to code it all and manage to verify that everything works according to expectations. Every once in awhile, there are still bugs with how one ability interacts with another. You can plan it all out, but it has got to be easy to miss something. Too many interactions! :)

swanson3• 10 years ago

A great anecdote in the 'we can't test this code' discussion -- for an aggressive two-week release cycle of this massively popular game, this level of testing has probably paid for itself many times over.

dimino11• 10 years ago

In this case? Probably. But the idea that catching a bug in production is a huge problem is a myth, pushed by research that was later completely withdrawn.

debaserab2• 10 years ago

When customers discover bugs before you do, it reflects poorly on your reputation and harms the trust you have established with the consumer of your application. That's not a myth.

swanson3• 10 years ago

Are you referring to research on the 'cost of change curve' or research on the economic impact of production bugs?

jnardiello• 10 years ago

But the idea that catching a bug in production is a huge problem is a myth

You clearly have never worked in fintech, banks or payments. I personally witnessed the moment we catched a race condition which costed the company n-k euros in missed transactions.

And this isn't even considering mission critical software where bugs can (literally) kill.

developer23• 10 years ago

Depends on the bug. Sticking to League of Legends as an example, is it really the worst thing if they have to disable a champion for a day or two to fix a bug? Not really. It still happens fairly often, and the impact is inconvenient but it's not the end of the world. Now how about a bug that prevents logins or crashes the backend? This completely take the game offline.

These sort of downtimes hurt customer satisfaction and the bottom line. If serious issues arise often enough, customers lose confidence and patience and may leave your product for a competitor. And while you're offline trying desperately to rush a fix, you're losing revenue.

If the service/product you're offering has competitors, quality matters. Sometimes it's not even the measurable quality, but the perception your customers have. Find me a business owner who thinks major bugs in production are not "a huge problem".

jakevoytko• 10 years ago

It definitely has. League of Legends is considered a serious e-sport game. Individual tournaments for League of Legends have $2,000,000+ prize pools. If a new bug decided a round of the tournament, it would undermine LOL as a serious contender for this type of attention. There is a terrific business case for investing the time to make this game as stable as possible.

mashlol• 10 years ago

This has actually happened before at official League of Legends tournaments (that is, a fairly serious bug in a serious match). I believe their policy in the case of a serious bug is to re-do the match, but I am not 100% sure.

ReadingInBed• 10 years ago

This actually happened last year at their biggest tournament. A well known bug caused several champions to be disabled midway through the tournament. This happens regularly that champions are disabled due to bugs at international events.

yokohummer7• 10 years ago

A release cycle of two weeks looks miracle to an outsider like me. Good to see what's going on internally. I loved the video showing automated champion moves, show me more! Also,

In Wood 5 we don't use wards anyway, so I see no problem with this critical failure

100% agreed. There's no point in changing to lens because nobody buys a ward!

cpeterso• 10 years ago

I'd love to hear more about automated stress testing and LoL's release schedule. Do they have beta releases or code freeze before the two week release dates?

badloginagain6• 10 years ago

If using an svn/p4 source control method, they probably branch mainline into a release branch, test, then branch to a staging, test against production data, etc, all the while fixing any necessary bugs. This allows development work to continue on mainline while keeping the release testing continuous and stable.

huac2• 10 years ago

They have a public beta environment that is set up for feature testing, rather than stress testing. The PBE does see code rollbacks (if features are incomplete) before releases, so I believe the game logic on the PBE represents basically what will be moved to the live server.

finishingmove4• 10 years ago

We see the test checks three things:

  Verifies:
    - KogMaw deals less damage to non-lane minions
    - KogMaw deals percentile magic damage
    - KogMaw deals normal damage to lane minions

and the verify method has three assertions. In my opinion, this should be three tests, each with only one assertion.

swanson3• 10 years ago

I tend to agree, but sometimes in these kind of instrumented test environments, the setup cost of each test case might be very high so maybe the team found it reasonable to group all the assertions into a single test (especially given that the suite is already taking 1-2 hours to give feedback to developers).

badloginagain6• 10 years ago

It appears they're grouping by ability.

finishingmove4• 10 years ago

I am well aware of that and I agree on being pragmatic, but more often than not, the reason for multiple assertions per test is developer laziness and/or unawareness of the benefits of isolating failures by having just one assertion per test.

d0100• 10 years ago

They'd soon be drowning in individual tests. And it wouldn't necessarily fit to separate them, considering all those 3 have to be tested on each skill usage. One shot has to obey those 3 rules.

Making each an individual test would triple the test time, pollute the test codebase and not bring any advantage.

chrislloyd• 10 years ago

The advantage in splitting up the assertions is that you get more visibility. If one test fails and not the other two that's extra information you can use to debug you wouldn't have if you have all 3 in one test.

finishingmove4• 10 years ago

Making each an individual test would triple the test time, pollute the test codebase and not bring any advantage.

Would it really? None of what you said here is true.

dimino11• 10 years ago

The code itself isn't super duper pythonic, which is not ideal, but definitely the right direction for a project like this to move.

It's just hard sometimes to set and follow standards when you're pushing to demonstrate value. Not impossible, but hard.

derFunk• 10 years ago

Wow, this is pretty sophisticated and commendable. I'd love to have the resources to do something similar. In contrast to 'standard' application development, automated testing is really rare in the non-AAA games industry. At least in terms of logic-/active gameplay testing. It's pure luxury, you can only do it if you can afford it. In a project-based work for hire game shop this is an almost unthinkable thing to do, because you don't get it sold to your contractors/customers. They just won't pay for the effort you don't our directly into the game. The only thing you can do is to develop your own automated testing framework over time and over projects, which is a tedious thing to do because you cannot really focus on it (because it's not a first class citizen in your project schedule).

badloginagain6• 10 years ago

I hope it started as a much more humble tool, that kept growing in size as the company did. Each release it gets a bit more useful, until you hit that critical mass point where's it's a pillar of development.

andrepd• 10 years ago

And yet they can't rewrite their ridiculously inefficient launcher properly :^)

quaunaut• 10 years ago

Actually, the launcher was replaced under 2 years ago. The matchmaking client has entered alpha, and is accompanied with rewrites to a lot of Riot systems to help it all work together.

huac2• 10 years ago

On the other hand, just because you have a great testing framework, it doesn't mean you should launch new game features/changes left and right.

(LoL is structured around roughly yearly 'seasons' for competitive play and for ranked play rewards. This season they have released a far greater amount of game mechanic changes, which make it difficult to plan competitive strategy and difficult for regular players to keep up.)

mangix2• 10 years ago

too bad dota 2 is a better game

dylz• 10 years ago

really, this stuff goes on even on HN?

errantspark2• 10 years ago

Maybe we extend the benefit of the doubt and perceive the comment as a reminder that having code that passes all the tests doesn't necessarily equate to having a good product?

It's obviously a stretch as that guy's username is the name of a DotA hero, but hey, rose colored glasses are fun sometimes.

kawsper• 10 years ago

Funnily enough, the latest patch was rushed out by Valve, and it contained a lot of bugs and strange behavior.

Lots of bugs in Dota 2 seems to be happening because of manual testing.

errantspark2• 10 years ago

Not to say that DotA wouldn't benefit from more rigorous testing, but in Valve's defense I'd say that the complexity of interactions in DotA is far beyond LoL. Some of the bugs you're seeing might only arise in extremely rare situations.

DotA is balanced with creativity in mind. When an exploitative strategy is found the game is not changed to remove it but instead through some combination of tweaks and modifications, often to seemingly unrelated aspects it's made into something that's only situationally viable.

The reason the game is so deep/interesting is because this philosophy has been in place for many (10+) years now resulting in a game that's much more complex than pretty much anything else out there. DotA 2 retains edge case behavior that was present in the original Warcraft 3 mod. Things that were once engine limitations are now part essential parts of gameplay. Preserving these weird interactions instead of attempting to make the game more regular/comprehensible is one of the things that allows such a high level of creativity in competitive play. There's always a way you can outplay your opponent that's clever. In go parlance: there's always new tesuji to be found.

All that being said I think Riot's efforts here are quite laudable and DotA could certainly find benefit from more rigorous testing.

dosgonlogs• 10 years ago

This is a silly comment. A cursory search of "League of Legends Bugs" yields similar results, lots of bugs. In fact, the Mac Client was rendered completely unplayable less than a month ago, which may have been fixed by now. Valve employ people that build automated testing (which very well may have built a system used by Dota 2 devs), so I think your last statement could be incorrect, but either way it is speculation, unless you have a source for that.

exabrial• 10 years ago

Lol I love the haters.

mangix2• 10 years ago

i dunno i keep reading on the dota 2 subreddit how riot is ruining LoL and new players asking for advice.

stormbuilder• 10 years ago

This is not reddit. If you don't have something meaningful to contribute, please feel free not to post.

amleszk• 10 years ago

Wow this is the first time I've seen automation testing applied to a video game. 2 things struck me as really great from this:

- Staging area for their tests, so many times I've lost confidence in our test suite because of a flaky test. We then delete that test forever. Adding tests to a staging area to very that they are stable is a great compromise

- each test is a class, with 'setup', 'execute' 'verify' - makes the test a lot easier to read and refactor

bruxis• 10 years ago

This is beautiful.

Ameo• 10 years ago

Oh man with that kind of control of the game they could /certainly/ create some kind of sandbox mode.

The APIs that they have for testing alone are pretty incredible; I'd love to be able to play in a mode where you could change level on-demand, create dummy enemies, etc.

BuckRogers• 10 years ago

With LoL being the most popular video game in the world right now, it's also the most relevant game of all time. How they build and test it is fascinating.

I've played this game for 7+ years now and as a programmer love to hear about all this. A Rioter said a couple years ago that they used Erlang[0] and as a longtime Erlang (and now Elixir) admirer and tinkerer that was great to know my favorite game uses it.

[0]https://erlangcentral.org/scaling-league-of-legends-chat-to-...

Automated Testing for League of Legends

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