jest-partial

Partial Matcher for Jest Expect

jest-partial asserts that the provided object is a subset of the expected. We don’t always want to verify the entire object that has been given. We often just want to protect the properties that we need, and ignore everything else.

Installation

With npm:

npm install --save-dev jest-partial

With yarn:

yarn add -D jest-partial

Setup

Jest >v24

Add jest-partial to your Jest setupFilesAfterEnv configuration. See for help

"jest": {
  "setupFilesAfterEnv": ["jest-partial"]
}

Jest <v23

"jest": {
  "setupTestFrameworkScriptFile": "jest-partial"
}

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('jest-partial');
require('jest-chain');
require('any other test framework libraries you are using');

Then in your Jest config:

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

Typescript

If your editor does not recognise the custom jest-partial matchers, add a global.d.ts file to your project with:

import 'jest-partial';

API

The examples below use the following data object:

const kitchen = {
  version: '1',
  floor: {
    material: 'wood',
    color: 'walnut',
  },
  drawers: [
    {
      contents: [
        { type: 'spoon', count: 4 },
        { type: 'fork', count: 2 },
      ],
    },
  ],
};

.toMatchPartial(object)

case: Our kitchen has multiple drawers, and we just want to know that there is at least one drawer that contains spoons.

expect(kitchen).toMatchPartial({
  drawers: [
    {
      contents: [{ type: 'spoon' }],
    },
  ],
});

case: Our kitchen has multiple drawers, and we want to know that there is a drawer that holds 2 forks.

expect(kitchen).toMatchPartial({
  drawers: [
    {
      contents: [{ type: 'fork', count: 2 }],
    },
  ],
});

case: Our kitchen has multiple drawers, and we want to know that there is a drawer that holds forks and spoons.

expect(kitchen).toMatchPartial({
  drawers: [
    {
      contents: [{ type: 'fork' }, { type: 'spoon' }],
    },
  ],
});