Today, I found a bug before I noticed it. Like, it was subtle, and so I wasn’t quite sure I saw it–maybe I hadn’t hit refresh yet? Later, I looked at the trace of my function and boom, there was a clear bug. Here’s the function with the bug. It responds to a request to …
It is better to practice risky things often and in small chunks with a limited blast radius, rather than to avoid risky things. Charity Majors, “Test in production? Yes“ Charity is writing about deploys. Not-deploying may be safer for tonight, but in the medium term it leads to larger deploys and bigger, trickier failures. In …
TL;DR: Study all the interactions between people, code, and our mental models; gather data and we can make real improvements instead of guessing in our retros. Software is hard to change. Even when it’s clean, well-factored, and everyone working on it is sharp and nice. Why? Consider a software team and its software. It’s a …
Read moreCode and Coders: components of the sociotechnical system
How important is correctness? This is a raging debate in our industry today. I think the answer depends strongly on the kind of problem a developer is trying to solve: is the problem contracting or expanding? A contracting problem is well-defined, or has the potential to be well-defined with enough rigorous thought. An expanding problem …
Elm is perfectly suited to property testing, with its delightful data-in–data-out functions. Testing in Elm should super easy. The tooling isn’t there yet, though. This post documents what was necessary today to get a property to run in Elm. Step 1: elm-test This includes an Elm library and a node module for a command-line runner. The library …
Darn side-effecting programs. Programs that change things in the outside world are so darn useful, and such a pain to test.For every piece of code, there is another piece of code that answers the question, “How do I know that code works?” Sometimes that’s more work than the code itself — but there is hope. …
“Quality software.” It means something different to everyone who hears it. You know quality when you see it, right? Or maybe when you smell it. Like a good perfume. Perfume preferences are different for everyone, and quality means something different for every application. In perfume, we can discover and describe our preferences using the Fragrance …
For unit tests, it’s handy to mock out side-effecting functions so they don’t slow down tests.[1] Clojure has an easy way to do this: use with-redefs to override function definitions, and then any code within the with-redefs block uses those definitions instead. To verify the input of the side-effecting function, I can override it with …
After moving from Scala to Clojure, I miss the types. Lately I’ve been playing with Prismatic Schema, a sort of optional typing mechanism for Clojure. It has some surprising benefits, even over Scala’s typing sometimes. I plan some posts about interesting ones of those, but first a more ordinary use of types: locating errors. Today …
Today, I wanted to write a post about code that sorts a vector of maps. But I can’t write that without a test, now can I? And not just any test — a property-based test! I want to be sure my function works all the time, for all valid input. Also, I don’t want to …