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Category: Programming (Page 1 of 3)

The simplest dependency injection

Consider a method that calculates some ETA:

class Calendar {
  add3WorkingDays(): Date {
    const result = new Date();
    let daysAdded = 0;
    while (daysAdded < 3) {
      result.setDate(result.getDate() + 1);
      if (this.isWorkingDay(result)) {
        daysAdded++;
      }
    }
    return result;
  }

  isWorkingDay(date: Date): boolean {
    const day = date.getDay();
    return day !== 0 && day !== 6;
  }
}

Notice how add3WorkingDays depends on the time when it’s called (result is initially now). Because of that, you’d have trouble writing reliable unit tests for this.

My recommendation: change the implicit dependency of now to explicit one and inject it:

  add3WorkingDays(date: Date): Date {
    const result = new Date(date);
    // no changes from here

It takes only so much to implement dependency injection, the most overcomplicated technique in the history of programming. You don’t need frameworks, containers, service locators, interfaces, or decorators. You only need to know how to parameterize a method.

Oh, by the way, we changed the interface of the method too. We have to change all the callers: calendar.add3WorkingDays() -> calendar.add3WorkingDays(new Date())

Does this mean you don’t want to introduce dependency injection later in the project, to avoid risky refactors? No. You can still have DI without changing the interface using the default parameter:

  add3WorkingDays(date: Date = new Date())
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Unit tests can (and should!) go through many classes

We often design our code so that one procedure comprises many classes, often grouped by layers. For example, in web dev, that could be controllers, models, repositories, etc:

Layers are good. Often at least two layers are desirable for maintainability: domain and low-level. If you’re like me, you like 2-5 layers but not too many.

Now how do you test such code? It comes naturally to want to test each component separately and mock out the collaborators from other layers. I believe it’s because unit tests are said to be run “in isolation”:

My advice – don’t automatically do this. Aim for this instead:

Why is it better?

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🎉 Puzzle Balls Release 🎉

I have the pleasure to announce: the playable release of Puzzle Balls is out! Go ahead, play it! Prepare your arrow keys and space bar, and connect 3 or more; fullscreen recommended!

Puzzle Balls early release gameplay preview

The game is not developed only by me. I collaborate with a dear friend of mine, Michał Hołowaty.

Keep in mind it’s a very early release. There is not much depth to the gameplay, plus many assets are just a placeholder, and many features are in the early stages. Although the game is fully functional and can be highly addictive! You have been warned!

We keep having fun playing and developing the game, so save the link in your bookmarks and come back to it once in a while. You are likely to encounter new features soon!

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“Automate everything” is a scam

Nowadays I see people going crazy about automation. Everything must be in Docker containers, If it’s not in docker, I ain’t touch it.

Every task must be performed on the CI server, every repetitive task must be converted to a script, nothing in the MVP can the back office do manually. People are praised when they claim: “automate everything”!

I am on the very opposite side. I think automation generally isn’t worth it. It can be harmful to your project and see the trend of “automate everything” kinda crazy. Let me explain why.

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