chai-match-pattern

What is chai-match-pattern?

The chai-match-pattern package is a plugin for the Chai assertion library that allows for pattern-based matching of objects. It is particularly useful for testing complex data structures where exact matches are not necessary, and patterns can be used to validate the structure and content of the data.

What are chai-match-pattern's main functionalities?

Pattern Matching

This feature allows you to use lodash predicates to define patterns that the actual data should match. In this example, the actual object is checked against a pattern where 'id' and 'age' should be numbers and 'name' should be a string.

const chai = require('chai');
const chaiMatchPattern = require('chai-match-pattern');
const _ = chaiMatchPattern.getLodashModule();
chai.use(chaiMatchPattern);

const expect = chai.expect;

const actual = {
  id: 123,
  name: 'John Doe',
  age: 30
};

const pattern = {
  id: _.isNumber,
  name: _.isString,
  age: _.isNumber
};

expect(actual).to.matchPattern(pattern);

Partial Matching

Partial matching allows you to specify only a subset of the properties that need to be matched. In this example, the pattern only specifies that 'id' should be a number and 'address.city' should be 'New York', ignoring other properties.

const actual = {
  id: 123,
  name: 'John Doe',
  age: 30,
  address: {
    city: 'New York',
    zip: '10001'
  }
};

const pattern = {
  id: _.isNumber,
  address: {
    city: 'New York'
  }
};

expect(actual).to.matchPattern(pattern);

Custom Pattern Matching

Custom pattern matching allows you to define your own functions to validate the properties. In this example, the 'id' should be greater than 100 and 'name' should start with 'John'.

const actual = {
  id: 123,
  name: 'John Doe',
  age: 30
};

const pattern = {
  id: (val) => val > 100,
  name: (val) => val.startsWith('John')
};

expect(actual).to.matchPattern(pattern);

Other packages similar to chai-match-pattern

chai-subset

chai-subset is a Chai plugin that allows for partial matching of objects. It is similar to chai-match-pattern in that it allows you to assert that an object contains a subset of properties. However, chai-subset does not support the use of predicates or custom functions for matching, which makes chai-match-pattern more flexible for complex pattern matching.

chai-like

chai-like is another Chai plugin that provides similar functionality to chai-match-pattern by allowing pattern-based matching of objects. It supports partial matching and custom matchers, but it is less focused on using lodash predicates, which is a key feature of chai-match-pattern.

jest

Jest is a popular testing framework that includes built-in support for pattern matching with its 'expect.objectContaining' and 'expect.arrayContaining' matchers. While Jest is a full testing framework, chai-match-pattern is a specific plugin for Chai, making it more suitable for projects already using Chai.

README

chai-match-pattern

Related Modules:

chai-match-pattern is a Swiss Army Knife for deep matching JSON objects. It is essentially a Chai wrapper for lodash-match-pattern and detailed documentation can be found there about its pattern matching functionality. This functionality includes deep matching of JSON properties by

• Exact values
• Regex
• Any matcher from checkit (e.g. _.isURL, _.isEmail)
• Any matcher from lodash (e.g. _.isObject, _.isNaN)
• Partial matches
• Custom matching functions
• Filtered values
• And more...

Basic Usage

# with npm
npm install chai-match-pattern --save-dev
# or with yarn
yarn add --dev chai-match-pattern

In your test file insert

const chai = require('chai');
const chaiMatchPattern = require('chai-match-pattern');
chai.use(chaiMatchPattern);
const _ = chaiMatchPattern.getLodashModule(); // recommend using our lodash extension

Then use patterns to check your JSON with the .matchPattern(pattern) assertion function. For example

chai.expect({a: 1, b: 'abc'}).to.matchPattern({a: 1, b: _.isString});

See lodash-match-pattern for way, way more details.

Additionally any of the included isXxxx functions can be used directly as assertion functions. For example

chai.expect(7.5).isBetween(7, 8);