object-boolean-combinations^6.1.19

Installation

Quick Take

Purpose

This function generates an array of all possible variations, 2^n, of n boolean options object keys. It’s used for unit-testing purposes. For example,

detergent has 12 boolean toggles — that’s 2^12 = 4096 variations to test for each input.

string-collapse-white-space has 6 boolean toggles — that’s 2^6 = 64 variations to test.

And so on.

Our packages don’t use this library directly, there is a higher-level package test-mixer which takes into account non-boolean keys and uses this package to generate variations of boolean keys only, then restores the other keys.

API — combinations()

The main function combinations() is imported like this:

It’s a function which takes two input arguments:

The function will return an array of plain objects, each of a shape (the BoolObj type above):

API — version

You can import version:

Overriding

Sometimes you want to override the object keys, for example, in the a settings object, we want to override all a and b keys to be only true (1). This reduces the object combinations from 2^3 = 8 to: 2^(3-2) = 2^1 = 2:

import { combinations } from "object-boolean-combinations";
const test = combinations(
  { a: false, b: false, c: false },
  { a: true, b: true } // <----- Override. These values will be on all combinations.
);
console.log(`test = ${JSON.stringify(test, null, 4)}`);
// => [
//      {a: true, b: true, c: false},
//      {a: true, b: true, c: true}
//    ]

In example above, a and b are “pinned” to 1, thus reducing the amount of combinations by power of two, essentially halving resulting objects count twice. Notice how only c is having variations.

In practice

In practice, we use this overriding to perform the specific tests on Detergent.js. For example, let’s say, we are testing: does Detergent encode entities correctly. In that case we need two arrays filled with objects:

• first array — encodeEntities = true and all possible combinations of the other 9 settings (2^(10–1)=512 objects in array)
• second array — encodeEntities = false and all possible combinations of the rest — again 512 objects in array.

Here’s a unit test which uses objectBooleanCombinations() to create a combinations array of settings objects, then uses forEach() to iterate through them all, testing each:

test("encode entities - pound sign", (t) => {
  combinations(sampleObj, {
    convertEntities: true,
  }).forEach(function (elem) {
    t.equal(
      detergent("\u00A3", elem),
      "£",
      "pound char converted into entity"
    );
  });
});

Changelog