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11 best JavaScript Assertion libraries in 2025

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by marketing.admin@openweaver.com dot icon Updated: Mar 13, 2023

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Testing is a crucial part of the software development process. A good JavaScript testing tool helps you identify bugs and errors quickly and fix them as soon as possible. All modern JavaScript testing frameworks use assertion libraries to perform assertions about the content of the code being developed. Assertions are a set of behaviors that developers can use to test if the function produces the correct output or not. These assertions help analyze the program and see if it is working correctly or not. Here we list down 11 best JavaScript Assertion open-source libraries chai - TDD assertion framework; power-assert |- Power Assert; nodeunit - Easy unit testing.

chaiby chaijs

JavaScript doticonstar image 7902 doticonVersion:v5.0.0-alpha.0doticon
License: Permissive (MIT)

BDD / TDD assertion framework for node.js and the browser that can be paired with any testing framework.

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            chaiby chaijs

            JavaScript doticon star image 7902 doticonVersion:v5.0.0-alpha.0doticon License: Permissive (MIT)

            BDD / TDD assertion framework for node.js and the browser that can be paired with any testing framework.
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                      power-assertby power-assert-js

                      JavaScript doticonstar image 2775 doticonVersion:Currentdoticon
                      License: Permissive (MIT)

                      Power Assert in JavaScript. Provides descriptive assertion messages through standard assert interface. No API is the best API.

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                                power-assertby power-assert-js

                                JavaScript doticon star image 2775 doticonVersion:Currentdoticon License: Permissive (MIT)

                                Power Assert in JavaScript. Provides descriptive assertion messages through standard assert interface. No API is the best API.
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                                          nodeunitby caolan

                                          JavaScript doticonstar image 1913 doticonVersion:0.11.2doticon
                                          License: Permissive (MIT)

                                          Easy unit testing in node.js and the browser, based on the assert module.

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                                                    nodeunitby caolan

                                                    JavaScript doticon star image 1913 doticonVersion:0.11.2doticon License: Permissive (MIT)

                                                    Easy unit testing in node.js and the browser, based on the assert module.
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                                                              should.jsby shouldjs

                                                              JavaScript doticonstar image 1914 doticonVersion:13.1.3doticon
                                                              License: Permissive (MIT)

                                                              BDD style assertions for node.js -- test framework agnostic

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                                                                        should.jsby shouldjs

                                                                        JavaScript doticon star image 1914 doticonVersion:13.1.3doticon License: Permissive (MIT)

                                                                        BDD style assertions for node.js -- test framework agnostic
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                                                                                  better-assertby tj

                                                                                  JavaScript doticonstar image 279 doticonVersion:1.0.2doticon
                                                                                  License: Permissive (MIT)

                                                                                  c-style assert() for nodejs, reporting the expression string as the error message

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                                                                                            better-assertby tj

                                                                                            JavaScript doticon star image 279 doticonVersion:1.0.2doticon License: Permissive (MIT)

                                                                                            c-style assert() for nodejs, reporting the expression string as the error message
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                                                                                                      commonjs-assertby browserify

                                                                                                      JavaScript doticonstar image 258 doticonVersion:v2.0.0doticon
                                                                                                      License: Permissive (MIT)

                                                                                                      Node.js's require('assert') for all engines

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                                                                                                                commonjs-assertby browserify

                                                                                                                JavaScript doticon star image 258 doticonVersion:v2.0.0doticon License: Permissive (MIT)

                                                                                                                Node.js's require('assert') for all engines
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                                                                                                                          http-assertby jshttp

                                                                                                                          JavaScript doticonstar image 141 doticonVersion:1.4.1doticon
                                                                                                                          License: Permissive (MIT)

                                                                                                                          assert with status codes

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                                                                                                                                    http-assertby jshttp

                                                                                                                                    JavaScript doticon star image 141 doticonVersion:1.4.1doticon License: Permissive (MIT)

                                                                                                                                    assert with status codes
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                                                                                                                                              nightwatch-custom-commands-assertionsby maxgalbu

                                                                                                                                              JavaScript doticonstar image 135 doticonVersion:1.1.1doticon
                                                                                                                                              License: Permissive (MIT)

                                                                                                                                              Nightwatch.js custom commands and assertions

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                                                                                                                                                        nightwatch-custom-commands-assertionsby maxgalbu

                                                                                                                                                        JavaScript doticon star image 135 doticonVersion:1.1.1doticon License: Permissive (MIT)

                                                                                                                                                        Nightwatch.js custom commands and assertions
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                                                                                                                                                                  node-assert-plusby joyent

                                                                                                                                                                  JavaScript doticonstar image 119 doticonVersion:Currentdoticon
                                                                                                                                                                  License: Permissive (MIT)

                                                                                                                                                                  Extra assertions on top of node's assert module

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                                                                                                                                                                            node-assert-plusby joyent

                                                                                                                                                                            JavaScript doticon star image 119 doticonVersion:Currentdoticon License: Permissive (MIT)

                                                                                                                                                                            Extra assertions on top of node's assert module
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                                                                                                                                                                                      truffle-assertionsby rkalis

                                                                                                                                                                                      JavaScript doticonstar image 114 doticonVersion:v0.9.2doticon
                                                                                                                                                                                      License: Permissive (MIT)

                                                                                                                                                                                      🛠 Assertions and utilities for testing Ethereum smart contracts with Truffle unit tests

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                                                                                                                                                                                                truffle-assertionsby rkalis

                                                                                                                                                                                                JavaScript doticon star image 114 doticonVersion:v0.9.2doticon License: Permissive (MIT)

                                                                                                                                                                                                🛠 Assertions and utilities for testing Ethereum smart contracts with Truffle unit tests
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                                                                                                                                                                                                          babel-jest-assertionsby mattphillips

                                                                                                                                                                                                          JavaScript doticonstar image 92 doticonVersion:v0.1.0doticon
                                                                                                                                                                                                          License: Permissive (MIT)

                                                                                                                                                                                                          Babel Plugin that adds safety to your tests by verifying assertions are actually ran 🃏⁉️

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                                                                                                                                                                                                                    babel-jest-assertionsby mattphillips

                                                                                                                                                                                                                    JavaScript doticon star image 92 doticonVersion:v0.1.0doticon License: Permissive (MIT)

                                                                                                                                                                                                                    Babel Plugin that adds safety to your tests by verifying assertions are actually ran 🃏⁉️
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