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Comment by jshen | Hacker News Reader

"How will we prevent this bug from ever reaching customers again?"

I think the cost of this is far higher than it's worth.

Every so often you're right... you certainly should consider the costs of automating the test versus the risk of regressing.

But note that once you you have an organization good at writing tests, the incremental cost of writing a test is very, very small.

We like the term "10x" around here. Design systems for 10x the customers of today. Write code that will survive for a year. (Otherwise it may have been wasted.) Only fix bugs once so you can grow the engineering team without rehashing old issues.

Are you a programmer presently? That works on a codebase that's at least in the tens of thousands of lines of code?

Tell me what software you write so that I know to never, ever use it.

I'll play along. Have you ever owned your own business, and had to make the trade off between absolute quality and efficiency?

The one between correct and works-for-the-customer?

lines of code is very dependent on the language. I have one rails app that's in the 5k range, excluding tests, and it's been running for over a year with no restarts and no need for bug fixes. I think that says something about the effectiveness of my process.

I question the design decisions of any code base with tens of thousands lines of code.

If your app has been running for over a year, you might want to look into this (before someone else does)... http://groups.google.com/group/rubyonrails-security/msg/7f57...

thanks for the pointer. the site wasn't affected by that.

> I question the design decisions of any code base with tens of thousands lines of code.

What operating system are you running on?

my servers are either debian or ubuntu, and my laptop is a mac. You do realize that the OS isn't a single monolithic code base. It's a bunch of smaller code bases that work together, which is precisely the point I was making.

Want to take a guess at how many lines of code are in the Linux kernel?

that's the exception, not the rule right? It's also a example of something that I would absolutely write thorough tests for.

I'm also curious how modular it is. Does a kernel hacker have to keep the structure of that whole set of code in his/her head? I'm guessing there are a lot of clean seams in it that in practice reduce the actual lok related to a project down to a much smaller number.

This is from linus' chapter in "open sources"

"With the 2.0 kernel linux really grew up a lot. This was the point we added loadable kernel modules. This obviously improved modularity by making an explicit structure for writing modules. Programmers could work on different modules without risk of interference."

Meaningless. You made an explicit statement that you thought all code bases with more than 10 k lines have "questionable design", using a piddly little rails app as an example.

When someone pointed out that linux kernel had millions of lines now you are retreating to "but it is modular". Programming languages have had modules since the eighties. If someone points out a 25,000 line module what will you say? Each function has less than 10 k lines?

The point is that there are well designed code bases (the design includes modularization) with sizes well above 10 k lines , which directly contradicts your point. I've worked on well designed enterprise systems with a few million lines of code.

You've flipped my statement which changes its meaning. I said I'd question the design of any code base that large. Some would pass that questioning. I did not say that all large code bases have questionable design.

I won't debate a strawman anymore so I'll move on. Btw, are device drivers counted in that millions of lines of code? If so those are very independent things.

This thread was about test coverage, how many of those millions of lines of kernel code are covered by a unit test?

EDIT: so you agree with my original assertions that large test suites may not be worth the cost?

"how many of those millions of lines of kernel code are covered by a unit test? "

Not many. And yet the kernel is an awesome piece of code. That was the point. I don't have the time to debate test-driven/test-coverage fanatics either.

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