chai-subset

What is chai-subset?

chai-subset is a plugin for the Chai assertion library that allows you to assert that a JavaScript object contains a subset of properties. This is particularly useful for testing partial matches in objects, arrays, and nested structures.

What are chai-subset's main functionalities?

Object Subset Matching

This feature allows you to check if an object contains a subset of properties. In the example, the object `obj` is checked to see if it contains the properties `a` and `b` with the specified values.

const chai = require('chai');
const chaiSubset = require('chai-subset');
chai.use(chaiSubset);
const expect = chai.expect;

const obj = { a: 1, b: 2, c: 3 };
expect(obj).to.containSubset({ a: 1, b: 2 });

Array Subset Matching

This feature allows you to check if an array contains a subset of objects. In the example, the array `arr` is checked to see if it contains objects with the properties `a` and `b`.

const chai = require('chai');
const chaiSubset = require('chai-subset');
chai.use(chaiSubset);
const expect = chai.expect;

const arr = [{ a: 1 }, { b: 2 }, { c: 3 }];
expect(arr).to.containSubset([{ a: 1 }, { b: 2 }]);

Nested Object Subset Matching

This feature allows you to check if a nested object contains a subset of properties. In the example, the nested object `nestedObj` is checked to see if it contains the nested properties `a.b.c` with the specified value.

const chai = require('chai');
const chaiSubset = require('chai-subset');
chai.use(chaiSubset);
const expect = chai.expect;

const nestedObj = { a: { b: { c: 3 } } };
expect(nestedObj).to.containSubset({ a: { b: { c: 3 } } });

Other packages similar to chai-subset

chai-things

chai-things is a Chai plugin that provides additional assertions for arrays. It allows you to assert that all or some items in an array meet certain conditions. Compared to chai-subset, chai-things is more focused on array-specific assertions rather than general object subset matching.

chai-as-promised

chai-as-promised is a Chai plugin that extends Chai with assertions about promises. It allows you to assert that a promise will be fulfilled or rejected with a specific value. While it doesn't provide subset matching, it complements chai-subset by adding promise-specific assertions.

chai-json-schema

chai-json-schema is a Chai plugin that allows you to validate JSON objects against a JSON schema. It provides a way to assert that an object conforms to a specific schema, which can be more powerful than subset matching when you need to validate complex structures. Compared to chai-subset, chai-json-schema offers more comprehensive validation capabilities.

README

chai-subset

"containSubset" object properties matcher for Chai assertion library

Installation

npm install --save-dev chai-subset

Usage

common.js

var chai = require('chai');
var chaiSubset = require('chai-subset');
chai.use(chaiSubset);

in your spec.js

var obj = {
	a: 'b',
	c: 'd',
	e: {
		foo: 'bar',
		baz: {
			qux: 'quux'
		}
	}
};
	
expect(obj).to.containSubset({
	a: 'b',
	e: {
		baz: {
			qux: 'quux'
		}
	}
});

// or using a compare function
expect(obj).containSubset({
	a: (expectedValue) => expectedValue,
	c: (expectedValue) => expectedValue === 'd'
})

// or with 'not'
expect(obj).to.not.containSubset({
	g: 'whatever'
});

Also works good with arrays and should interface

var list = [{a: 'a', b: 'b'}, {v: 'f', d: {z: 'g'}}];

list.should.containSubset([{a:'a'}]); //Assertion error is not thrown
list.should.containSubset([{a:'a',  b: 'b'}]); //Assertion error is not thrown

list.should.containSubset([{a:'a', b: 'bd'}]); 
/*throws
AssertionError: expected
[
    {
        "a": "a",
        "b": "b"
    },
    {
        "v": "f",
        "d": {
            "z": "g"
        }
    }
]
to contain subset 
[ { a: 'a', b: 'bd' } ]
*/

and with assert interface

assert.containSubset({a: 1, b: 2}, {a: 1});