Holger's Blog

I am writing again. Mostly for myself. As a journal. In the future I’ll try things a bit differently around here: I want to share what I am thinking about, how I work and what I am working on (as far as it makes sense in regard to my clients and NDAs).

Working

I secured a new client for autumn and the first months of 2020. I’ll be joining them as interim tech lead. I am excited. This will let me work a lot with Rails again. The last months were JS/TS only…

Something that I was proud of during the last week was a caching solution I created. Let me describe it briefly:

• We are in a TypeScript project
• There are external APIs we are calling to populate our app with data.
• We display the same value in multiple places on a page or after navigating somewhere else.
• We do not have a global state management like Redux etc. (Why is a discussion for another time 😉)
• Every display of the value resulted in a fetch to the same API resource.

What I built was a cache-aside solution, where I cache the (pending) Promise for the first request. All subsequent requests receive this Promise as return value, without fetching again. Once the Promise is resolved, the value appears where it’s supposed to appear and every requests happens just once. This is possible and makes sense, because the values change very infrequently and using the “old” value until the site is reloaded works just fine. We don’t yet need things like etags and ModifiedSince. But perhaps this will be added in a future situation. Anyway, this was cool and also challenging to find a proper solution. Caching the Promise itself was an idea that was developed together with my co-worker, Franz.

I am redesigning my website these last months. It always takes longer, because nobody pays me for that 😂. It’s progressing nicely, thanks to the help of my designer. She’s great. I am really looking forward to sharing this with you. Also, I need to get back into the rhythm of writing articles. I have a lot of topics planned and see my traffic increase steadily.

I did not renew my subscription to the email marketing service Drip that I used during this last year. They were too expensive anyway. You will receive this mail through Drip, still. But future mails might be sent by something else. I’ll keep you posted and hope to be able to complete the migration without any hassle for you.

Personal

I am in the middle of a training program for my next 10 kilometers race. It’s quite intense, I am running 4-5 times a week. To make the time for that I started to do run-commutes. This means I run to my client in the morning, take a shower there and run home in the evening/afternoon. This is demanding but works out quite nicely. The shortest distance to my current client is about 6km, so it’s fine to run it twice.

I have a height-adjustable desk at my home office now and it is awesome. I love the flexibility. I actually stand most of the time. But after lunch, for example, I tend to sit down more. Ha, just wanted to share. If you are on the fence about getting one, you should!

Thinking / Reading

A quote that still makes me think:

Recently, one of my favorite questions to bug people with has been “What is it you do to train that is comparable to a pianist practicing scales?” If you don’t know the answer to that one, maybe you are doing something wrong or not doing enough. Or maybe you are (optimally?) not very ambitious?

It’s from this article: https://marginalrevolution.com/marginalrevolution/2019/07/how-i-practice-at-what-i-do.html

My current answer is “my side project” I am working on (nothing to share publicly here, yet). But I do know that I am not stretching doing that project. Compared to my run training, this is like a relaxed long run. Important for basic fitness and healthy, but nothing that increases my ability by much. The caching solution I wrote about certainly stretched me and I learned new things there. But this was work and not practice. And not deliberate but a happy “accident”. I should be able to plan for these training sessions.

So this is something I am thinking about.

Holger

If you work on your branch you run into the situation that you would like to push your changes to the remote repository. CI will then pick up your changes and run the linting and code quality checks on it. Afterwards, you will see whether you improved the quality. But perhaps there are some new violations that crept into the code? Happens to all of us!

I usually like to see and check if any new issues might come up on CI. This lets me improve them before I push. The checks I run locally depend on the kind of work that I do. Lately that’s a lot of Ruby on Rails again — which is great. I love that framework and the language. To grade my code, I use Rubocop, Reek and Flay. If you run their respective commands on your repository, they will check the whole code base. This might be ok, if you didn’t have any issues before. Since I join teams, these days, that work on legacy projects it is rare that there are no problems with the code. If I run the commands just so, I will get a long list and couldn’t possibly see the issues that I introduced through my changes. Lucikly, there is Git and some “command line foo” that can help us here:

git fetch && git diff-tree -r --no-commit-id --name-only master@\{u\} head | xargs ls -1 2>/dev/null | grep '\.rb$' | xargs rubocop

This command will fetch the current state from the remote and diff your branch/changes to master branch. It then runs rubocop on these changes. In my ~/.aliases.local file I added three lines for all three linters.

# Code Quality
alias rubocop-changes="git fetch && git diff-tree -r --no-commit-id --name-only master@\{u\} head | xargs ls -1 2>/dev/null | grep '\.rb$' | xargs rubocop"
alias reek-changes="git fetch && git diff-tree -r --no-commit-id --name-only master@\{u\} head | xargs ls -1 2>/dev/null | grep '\.rb$' | xargs reek"
alias flay-changes="git fetch && git diff-tree -r --no-commit-id --name-only master@\{u\} head | xargs ls -1 2>/dev/null | grep '\.rb$' | xargs flay"

I am still working on a way to just call one command and have all thee commands run. That doesn’t yet work. Probably because of exit-code reasons, when one linter finds issues.

These simple commands offer a convenient way to find local issues and correct them before pushing to CI.

A few weeks ago I wrote about deleting your tests. Yesterday I received the weekly email from Avdi Grimm, where he touches on this subject.

Some premises about my relationship with unit testing:

I like test-driven development. I like driving out individual object design small, isolated (e.g. no database) unit tests. I think of these unit tests as a design aid, full stop. Any help they provide with preventing regressions is gravy. I treat unit tests as disposable. Once they have served their purpose as design aids, I will only keep them around so long as they aren’t getting in the way. These four premises are strongly interconnected. Take away #1 (test first), and tests are no longer a design aid and none of the other points are valid. Take away #2 (isolation) and we get into integration test territory where there’s a much higher possibility of tests having regression-prevention value. Take away #3 (design focus) and the other points lose their justification. Take away #4 (disposability) and I spend all my time updating tests broken code changes.

This makes it easy for me to find myself at cross purposes with others in discussions about unit testing, because often they come into the conversation not sharing my premises. For instance, if your focus in unit testing is on preventing regressions, you might well decide isolated unit tests are more trouble than they are worth. I can’t really argue with that.

A recent conversation on this topic inspired the thought from the driving-design perspective, maybe unit tests are really just a crutch for languages that don’t have a sufficiently strong REPL experience. While I don’t think this is strictly true, I think the perspective shines a useful light on what we’re really trying to accomplish with unit tests. I almost think that what I really want out of unit tests is the ability to fiddle with live objects in a REPL until they do what I want, and then save that REPL session directly to a test for convenience in flagging API changes.

That conversation also spawned the idea of immutable unit tests: unit tests that can only be deleted, never updated. A bit like TCR. I wonder if this would place some helpful incentives on the test-writing process.

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