Comment by sreque | Hacker News Reader

Comment by sreque | Hacker News Reader

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It's a very short-sighted view on testing, although I'm not surprised SREs would say it. The biggest problem with software deployment is that it is owned and managed by people who have no vested interest in developer productivity, including devops engineers.

A major goal of any org should be developer productivity; otherwise you are just hemorrhaging money and talent. When I say developer productivity, I mean: How confidently and quickly can I make a shippable, rollback-free change to a unit of software?

If you are the dos equis man of testing, "I don't always test my code, but when I do, I do it in production", then you can't confidently make any change without risking a production outage, so you play lots of games, like you mentioned, around canarying, rolling out to a small percentage of users, etc., but at the end of the day your developer productivity has absolutely tanked.

The goal of any system maintenance should be that a developer can quickly make and test a change locally and be highly confident that the change is correct. The canarying, phased rollouts, and other such systems should not be the primary means of testing code correctness.

Yeah, I really appreciate excellent rollout strategies, although I suspect a lot of them are more developed out of self defense by SRE teams. I see it as a series of safety nets: I'm still going to write tests for my code so that I don't have far to fall if I make a mistake. But I also want a safe rollout so if I miss the first net I don't splatter on the pavement.

And I totally agree with out about developer productivity. It's just not a consideration in most places. For example, in a factory or a restaurant, meetings are things that happen rarely and in constrained time slots, because everybody realizes that production is primary. But in most software companies, actually getting work done is second priority to meetings.

Agreed. I was an SRE for over a year and the philosophy is that anything that is shipped can be broken. SRE is all about detecting, limiting, and mitigating damage. I think this is the right philosophy for SREs but should not be the total picture in the org.

I am also agreed in that I anecdotally often see a disregard for automated testing. I am still trying to understand how to eliminate this tendency. I know that in every software project I've had a major hand in building, I've helped ensure automated testing, with a heavy emphasis on unit testing, become a major part of team culture, and I've always felt the tests more than paid for themselves over time, even in the relative short-term.

For sure. I'm still trying to understand it too. Two things that have helped me:

To contain time pressure, I like a kanban board with small units of work. If the team has a history of steady delivery of small lumps of useful stuff, managers are more willing to trust that we know what we're doing.

To mitigate the natural human lack of humility, I start with the rule that every bug requires a test before fixing. People may act as if they won't make mistakes, but it's much harder to claim that when we have a live bug. And then I like to introduce pair programming. Collaboratively adding failing tests and fixing them (as with ping-pong pairing) makes it fun.

What approaches do you use to shift things over?

I find it's much easier for greenfield projects than existing projects because you can lead by example. Also, with these projects there are opportunities to define team rules and culture for the project from the beginning.

Perhaps the greatest inertial force against improving test automation is the truth that any change to a in-production product incurs risk, coupled with the fact that adding tests often requires refactoring to make the code more testable. Techniques like writing tests as you refactor never get employed because there is resistance to any refactoring occurring at all in the first place. The general principle followed is: "make the smallest change possible to accomplish the objective".

I feel like overcoming these forces requires bravery from management or the team, coupled with a longer term vision for the project. For some projects, which are limping along on life support, it may not even be worth it to improve code quality. However, for most other projects I believe there is a better balance to be had between not unnecessarily breaking the product and not being afraid to make relatively risky changes to improve maintainability of the product.

Makes total sense. I do most of my work on greenfield projects for that reason.

But I think you're right. There's really no low-risk path when you have a poorly tested code base. You can keep letting productivity decline, which guarantees eventual project failure. You can do a giant rewrite, which is hugely risky. Or you can gradually dig yourself out.

There's still risk there, of course. But it's in smaller, more manageable lumps. It seems like the clearly superior path to me.

If the release/rollback process is fast enough, and your detection of anomalies is fast enough, you can still have great productivity, and few relevant outages, when testing in production. Hell, there are situations where testing outside of production is never going to cut it, as generation of sufficient load of the right shape would take you a whole lot more of engineering time than the consequences of failure.

That said, the tradeoffs are different for different companies, and different services in the same company: Within the same team at $large_company, I owned code where testing in production, via deployments and an amazing feature flag system, was better than unit tests, while there were other areas where the build system would dedicate many CPU-hours to testing before any release. To be able to have that flexibility though, you need to know your systems, know your problems, and have great tooling for both testing in production and extremely parallelized test suites. Small and medium sized companies might not have either alternative, and we had both!

So what I'd say is that any general rule on what should be the primary means of testing code correctness is going to not lead to optimal productivity, and even more so if you don't have top quality of tooling across every possible dimension. It's perfectly OK to argue about specific examples, but without judgement of this kinds of things without having the entire story of what's there is just hubris.

I unfortunately can't agree with that sentiment. If I have to rely on production traffic to test my feature, then, at minimum, my feedback cycle is:

1) Make change. Think really hard about it to make sure it's correct.

2) put out code review.

3) get approval. Merge change.

4) CI pipeline builds and deploys to prod.

5) absent of alerts must mean it works?

Even if you have no QA environment and nothing between you and prod, I've rarely seen deployment to prod take less than 30 minutes. That's an hour feedback cycle. Contrast with:

1) write code.

2) write unit tests.

3) run tests locally.

The feedback cycle, especially when you get iterative, can get as low as single digit seconds. I run my tests and see a bug. I fix the bug, then re-run the tests. Similarly, for a more complex feature, I can break the feature down into multiple cycles of build, test, verify.

And that's not even accounting for the overhead of managing feature flags, which is not free. In the best case, you need to at least release a second PR to remove the feature flag when the feature is successful. At my previous employer, this step was often forgotten and resulted in real, consequential technical debt as it became harder to figure out how the product behaved based on which feature flags were turned off or on.

If you have an experience leads you to believe that production testing can more productive than local automated testing, I at least have never seen it occur in and I find it difficult to even imagine it being true.

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