Introduction

What is Betterer?

Making widespread changes to a codebase can be really hard! When trying to make a radical improvement to a lot of code, one of two things often happens:

1. You start a really long-lived branch that is difficult to maintain and often impossible to merge.
2. You and your team have some agreement to make the improvement slowly over time, but it is forgotten about and never really happens.

Betterer is designed to solve this problem! Betterer will help you make incremental improvements to your codebase, and stop you from moving further away from your goals.

How does Betterer work?

Betterer is built upon an idea popularised by snapshot testing, where the result of a test is saved in a file in your codebase. However, instead of a static value, Betterer keeps track of a value as it changes over time, and makes sure that the value changes how you want it to change!

When you want to make an improvement to your codebase, start by making a new test, defined in a .betterer.ts file:

// .betterer.ts
import { BettererTest } from '@betterer/betterer';
import { smaller } from '@betterer/constraints';

export default {
  'thing you want to improve': () =>
    new BettererTest({
      test: () => runMyTest(),
      constraint: smaller,
      goal: 0
    })
};

When you run Betterer for the first time it will store the result of your tests in a .betterer.results file:

// BETTERER RESULTS V2.
exports[`thing you want to improve`] = {
  value: `12345`
};

Whenever your tests run again, Betterer will compare the new result against the expected result. If it gets better, the .betterer.results file will be updated with the new result ✅! If it gets worse, your test will fail and Betterer will throw an error ❌!