Inspired by jest-sorted. This packages extends jest.expect with 1 custom matcher, toBeSortedBy

Examples

expect([{ id: 1 }, { id: 2 }, { id: 3 }]).toBeSortedBy({ key: 'id' });
expect([{ count: '10' }, { count: '5' }]).toBeSortedBy({
  key: 'count',
  descending: true,
  coerce: true,
});

With npm:

npm install -D @netly/jest-sorted-by  

With yarn:

yarn add -D @netly/jest-sorted-by  

Add @netly/jest-sorted-by to your Jest setupFilesAfterEnv configuration. See for help

For example, add the following to your package.json at the root level. See configuring jest for more info.

"jest": {
  "setupFilesAfterEnv": ["@netly/jest-sorted-by"]
}

If you are already using another test framework, like jest-chain, then you should create a test setup file and require each of the frameworks you are using.

For example:

// ./testSetup.js
require('@netly/jest-sorted-by');
require('jest-chain');
require('any other test framework libraries you are using');

Then in your Jest config:

"jest": {
  "setupTestFrameworkScriptFile": "./testSetup.js"
}

The following options can be passed as an object to alter the assertions behavior

• descending : boolean - Asserts the array is sorted in descending order. (Defaults to false)

expect([3, 2, 1]).toBeSortedBy({ descending: true });

• key : string - Will use the value from the passed key in an array of objects.

expect([{ id: 1 }, { id: 2 }, { id: 3 }]).toBeSortedBy({ key: 'id' });

• strict : boolean - Fails the assertion if a passed key option does not exist in the object. (Defaults to false) Note: will use undefined for all missing keys and equal values are considered sorted.

expect([{ id: 1 }, { id: 2 }, { id: 3 }]).toBeSortedBy({
  key: 'nothing',
  strict: false,
});

• comparator : function - A custom function to use for comparison. (Default comparison is a simple greater / less than). In some cases you may want to check values are sorted by a different condition. The function will take 2 elements from the array (a,b) and should return:

  • A negative number if a comes first.
  • A positive number if b comes first.
  • 0 if the values are sorted equally.

See the compareFunction of Array.prototype.sort for more info.

const doubleDigitsFirst = (a, b) => {
  if (a >= 10 && b < 10) {
    return -1;
  }
  if (b >= 10 && a < 10) {
    return 1;
  }
  return 0;
};

expect([10, 20, 1, 2]).toBeSortedBy({
  compare: doubleDigitsFirst,
});