Test Runner with Instant Actionable Results
Wallaby.js runs your JavaScript and TypeScript tests as you type, streaming results next to your code. It also feeds rich runtime context to AI tools to help you write and fix code faster.
- Instant Actionable
Feedback - Time Travel
Debugger - Practical
Test Insights
Why Wallaby?
Test run results and coverage update in real time, right next to your code. Tools like time travel debugging and value explorer help you fix issues fast without breaking flow. Basic testing framework extensions are to Wallaby what Notepad is to a modern editor.
The tool is insanely fast because it calculates and runs the absolute minimum set of tests affected by your code changes; often only a single test needs to be run. No other testing tool, not even in watch mode, is capable of operating at this level of precision and efficiency.
Wallaby MCP server and tools give AI agents live access to test results, runtime values, execution paths, coverage, and dependencies — letting them deeply understand your code and solve complex problems, not just analyze files.
There is no vendor, API or framework lock-in when using Wallaby.js, because the tool is a plugin for your existing testing/UI framework and IDE. You will always be able to run your tests without Wallaby.js if you need to.
Choose your weapons
For your React application, Wallaby can run your Jest tests in VS Code faster, provide a debugging experience that has been designed for your tests that works more efficiently, and provide realtime granular test results that are more helpful.
efficiency without wallaby
Move forward and backwards through your code to understand the conditions that led to a specific bug. Wallaby's Time Travel Debugger accelerates your edit, compile and debug loop by allowing you to jump to a specific line of code, view runtime values, edit-and-continue and step into, over and out of your code.
Tests run immediately as you type, on unsaved changes, and in parallel if needed, streaming results in real time. Wallaby knows how your code and tests relate, so after a change only the minimum set of tests need to re-run; no other tool is capable of operating like this. No matter how large your project grows, feedback is almost instant.
MCP Server and AI tools have access to live runtime values, execution paths, branch-level code coverage, and dependency graphs. Your AI assistant gets detailed insights into actual code behavior during test execution, enabling more accurate debugging and test generation. Works with Copilot Agent, Cursor, Claude Code, Windsurf, Cline, and more.
See the results of console.log and runtime variables in your editor, right next to your code. Show and copy expression values with editor commands, accessible using keyboard shortcuts. Wallaby's special comment format can also be used to evaluate expressions and includes the ability to measure code execution times.
Error messages are displayed right next to the code that caused them. Gutter indicators show if the current line of code is the source of an error, or if it's on the execution path of a failing test or error. Editor commands (with keyboard shortcuts) allow you to quickly navigate to the associated failing test or error source.
Indicators in the gutter of your code editor are constantly updated in realtime to display test coverage so you can quickly see which lines of code are fully covered, only partially covered or not covered at all. Editor commands can be used to toggle uncovered regions to see exactly which parts of your code have not been executed.
Wallaby's Smart Start and Exclusive Test Run features allow running only the test files that you are currently working on. When opening or editing test files, Wallaby will start running them. Running a limited set of tests is usually many times faster than running all tests within your project and provides a highly productive workflow.
Complex data structures are displayed in an expandable, tree-like view, providing effortless exploration of deeply nested data. Each log entry includes contextual information, aiding in quickly identifying the origin of values. Interactive runtime value graphs allow you to visually explore your data.
Test execution results are ergonomically displayed in your editor's output window. All tests that are currently failing are listed, along with errors, diffs/snapshots, error stacks and any console.log calls. The output window's hyperlinks allow you to navigate directly to files in your editor, for example to the exact error line, or to a broken test.
Inspect the code that your test is executing in a single logical view. Wallaby's Test Story Viewer allows you to see your test execution trace without having to jump between multiple functions or code files. It is ideal for both reading and debugging code. Quickly see covered lines of code, step into, over and out of your code, and view runtime values.
Wallaby's Test Profiler allows you to quickly record a test's CPU usage profile to analyze its runtime performance. In addition to your own test and code files, your external dependencies code is also profiled. You can quickly navigate to a section of code you want to review by clicking on the hotspot in the profile viewer.
When errors contain expected vs. actual values, Wallaby displays compact diffs in editor hover tips and in Wallaby's output window. A command allows you to see the diff in a side-by-side view. Jest snapshot test support includes editor commands to update snapshots for your current test, current file, or your entire project.
A strategic-level view of your project's tests and code coverage is available through a comprehensive side view. Open files in your editor from your browser as you explore your tests and code-coverage. Sort and filter by name, duration, passing / failing tests, and code coverage. You can also exclude code from coverage calculations.
How much will Wallaby help me?
We estimate that using Wallaby's basic features alone will make your coding 10.84% more efficient and will save you $2396 per year.
But don't take our word for it. See what our customers have to say below and try it for free to see for yourself.
10,000+ companies all over the world, including many Fortune 500 companies, have increased their productivity and output by using Wallaby.js.
Love writing tests but don't do it enough. It is so satisfying when all tests seem to cover all corner cases and pass. To make me write more tests I purchased a license for @wallabyjs because it makes writing tests even more satisfying and faster and gives you quick overviews.
— Tim-Hinnerk Heuer (@geekdenz) November 4, 2020
— Dave Brotherstone (@bruderstein) May 12, 2021Reminder that @wallabyjs is probably the most useful testing tool in the JS ecosystem.
The tool is first rate, but the support they offer is first class too.
(I have no affiliation with them, I just love it)
I can't stress enough how @wallabyjs (and Quokka.js) have been useful for the last project I've been working on. It feels like having a conversation with the code instead of fighting it.
— pcostesi (@pcostesi) October 2, 2020
Yes @wallabyjs is great for many reasons. One reason that is never mentioned is that it implicitly teaches Unit Testing and Test-driven Development. No amount of books, videos or tutorials on Unit Testing will do for you or your mentees what 1 week with Wallaby will do.
— Vim with your soul like ether (@joeldpalmer) October 21, 2020
— Mark Kvetny (@biowaffeln) January 11, 2022Decided to write a parser the other day using @wallabyjs and @GitHubCopilot
Such a dream combo! The whole experience was so effortless, it felt like cheating
To be honest, I used to think TDD was just a good idea in theory, but never had enough time to really use it on my work projects. That changed when I started using Wallaby.js. #DEVCommunity https://t.co/ZM4sKS0GCD
— DEV Community 👩💻👨💻 (@ThePracticalDev) July 19, 2020
Big up to the @wallabyjs team, your product rocks! What a bliss to have the live tests feedbacks when you practice TDD 🤩
— Stanislas Bernard (@bernanstard) October 23, 2019
Loving your work, you might enter my top-3 annual best spendings competition 🤑 pic.twitter.com/tki5ccM8go
— Jose 'Joshi' Raez 🏳️🌈 (@JoshiRaez) June 24, 2019Just tried Wallaby.js and Im a instafan. It needs a bit of configuration (but they have updated repos with sample configurations to get you up and running) but the feedback loop it generates while writting tests/TDD is just amazing.
Now I need this for every language plz.
— David Whitney (@david_whitney) October 20, 2019So, @wallabyjs is literally still the best tool in the whole javascript ecosystem. Especially now it's practically zero-config.
Just wish it could gracefully borrow #ncrunch's "break into first broken covering test at this line" feature.
Coding with @wallabyjs easily cut my development-to-complete time in half. Can't recommend it enough.
— Sean Matheson (@controlplusb) April 4, 2016
Yes, I write tests, a lot. Both unit tests using jest and integration/e2e using Cypress. Of great help is a tool called WallabyJS (it costs money, but I'm not benefiting from telling you). WallabyJS is a continuous test runner that turns writing test into a dopamine rush⚡️! pic.twitter.com/DhZDtytU0p
— Wilgert Velinga (@Wilgert) April 17, 2020
Going to heavily use @wallabyjs /quokka to show live results of examples. Such an amazing tool.
— 🎙️ johnlindquist 🎙️ (@johnlindquist) June 18, 2018
Just ordered a @wallabyjs + Quokka.js licence after a 15 days trial 🥳. These tools are so good ! How can we work without them 🙃 ?
— Raphaël Moreau 🚀 (@rphlmr) March 12, 2020
I have said this a bunch of times already. It stills needs a shoutout at least once a year.@wallabyjs adds so much productivity. Such a useful tool!
— Thomas Sattlecker (@ThomasS09) August 22, 2019
Using @wallabyjs has to be one of the best developer experience I've felt in quite a long time. Awesome! Wish I learned about it sooner.
— Jean-Philippe Sirois (@veksenn) May 9, 2018
And I love using @wallabyjs when unit testing . It is truly game changing
— Jonathan Marbutt (@jmarbutt) June 11, 2019
— Pavneet Singh Saund🚀 (@pavsaund) June 11, 2018The crazy feeling when you write code / tests for a few days and it all just works when you hook it up to the frontend.
Seriously loving the TDD experience with @wallabyjs #javascript #vscode #tdd
@wallabyjs I cannot believe how cool you are. I literally write more and better tests because of you. Everyone should use you. #javascript
— Deric Cain (@DericCain) August 6, 2017
I struggled for days trying to get a clean unit testing experience for Typescript. Finally tried @wallabyjs and got it working immediately and exactly what I wanted. All I do is open source dev but my time (and sanity) is well worth the price
— Phil Scott (@Philco78) June 22, 2018
@wallabyjs Just renewed my licence after (nearly) daily use for a year. You’ve made unit testing easy. Thanks & keep up the good work :)
— Josh White (@__JoshWhite) May 3, 2019
Wallaby.js is pretty wicked. Works surprisingly well even when mixing TypeScript and JavaScript in the same project. It's like have NCrunch for JS, but even more insight.
— Ben Sammons (@BenSammons) January 7, 2019
Web Dev has so many nice things. Latest discovery: Wallaby. Runs tests in the background, shows state right next to the code. https://t.co/2wCuVDDwu5
— Peter Steinberger (@steipete) August 20, 2025
If your new company is doing TDD, and you guys are not using @wallabyjs, you are definitely missing out! Look into it and spread the word in your team, you’ll be the new hero! The cost of licence is nothing compared to the productivity boost! pic.twitter.com/2NKkbHiwKy
— Daniel Ormeño (@danielormeno) April 6, 2019
I use @wallabyjs, it works great in VS Code (our unit tests themselves are mocha and chai).
— Mark Kawakami (@skippykawakami) April 16, 2019
Worked on reducing down the 30 second wait for 1800 angular unit tests to run in Karma. Got it down to, well, instant with @wallabyjs :D
— Andrew Shelton (@Sheltonial) March 4, 2015
Nice. For me the best tool is @wallabyjs. I can highly recommend it 😉
— Simon Hoss (@simonhoss88) May 27, 2019
Since I've bought @wallabyjs my code coverage went sky-high. Never thought that this would happen.
— Damian Kamiński (@_dkaminski_) March 21, 2016
Using live code comments /*?.*/ with @wallabyjs in VS @code to measure execution time while writing #js is a mind blowing experience.
— Pierre Arnaud (@epsitec) May 1, 2017
I believe that I have to mention at least once a month how freaking awesome @wallabyjs is. Been working with it for 2 years and still love it every day. Worth every penny and great support. Thx @ArtemGovorov
— Brecht Billiet (@brechtbilliet) December 13, 2017
Oh yeah! We use it in every @strongbrew_io workshop so far! #tdd
— Seth Blanchard (@SethBlanchard) December 5, 2019Do you write React components?
Do you unit test* them?
If so you might want to check Wallabyjs - https://t.co/SFYoUCGlsqIt has made my test writing significantly faster (and more fun!)
*I'm not fanatical about unit testing - sometimes I find it helpful
WallabyJS is beautiful.
— Jared McCluskey (@Kluskey) May 23, 2019
For me barrier to doing TDD has always been better tooling esp in large projects, @wallabyjs however has changed that for me
— Nimesh Gurung (@nimgrg) October 4, 2016
Just bought my @wallabyjs freedom licence. Its rare that a tool can have such a big impact on my workflow so quickly, I highly recommend it!
— James Henry (@MrJamesHenry) July 26, 2016
@wallabyjs you make every day working with javascript/typescript more rewarding. Awesome tooling!!!!
— Ken Snyder (@yankeeinlondon) August 13, 2017
the time has come to renew my @wallabyjs license. I have never spend $100 so happily. It remains my most important tool!
— Dave Benjamin (@zpydee) April 6, 2017
@wallabyjs Seriously great tool, esp running only changed tests/code. I have 1000+ tests & Karma was beginning to be really slow. Thanks.
— Christopher Carson (@chriscarson) December 11, 2016
Well damn, @wallabyjs is just plain awesome for JS testing and coverage. They can expect to sell us a bunch of licenses soon!
— Hilke Heremans (@HHeremans) January 28, 2016
I love your work! Doing original work on a field that's been pretty much stagnant since black/green screens were cool. 🙌
— Nir Benita (@NirBenita) March 29, 2017
Set up @wallabyjs with typescript for the VS @Code extension I'm working on. There should be something like this for every language, wow
— Cody Hoover (@hoovercj) January 15, 2016
. @wallabyjs is turning into the killer app for me in VS Code. Makes writing tests so much easier. Plus the visibility of test coverage it gives me in a huge enterprise test suite makes me feel like Sauron (in a good way of course!) pic.twitter.com/eeLj72xNSc
— Ben Smith (@8ensmith) April 19, 2021
— Cristian Echeverria (@cecheverri4) April 13, 2021Since I bought WallabyJs license. I'm a happier developer
Wallaby + React Testing Library = 🚀
Receive immediate feedback on your test coverage is great! I'm a spoiled dev.
If you're a Frontend Dev, go and do yourself a favor! https://t.co/sPDMct58aN
shout out to @wallabyjs Would have been even more difficult without the "INSTA-REPL" within the ide. Honestly, I think this has been my most favorite ide plugin in years!
— λ fp-apprentice (@fp_apprentice) April 7, 2021
wallaby is killing it again 😍. If you have a javascript testsuite, there is literally no good reason to not use this tool. https://t.co/xULtpwVLAC
— Thomas Sattlecker (@ThomasS09) January 27, 2021
Just purchased a license for @wallabyjs to use with @code. 100% worth the money, so pumped to make #TDD a more natural part of my workflow.
— Ben White (@whtouche) April 17, 2016
Been leaning on @wallabyjs recently. The inline symbols shown per test exposed some amazing optimisation opportunities (and a few bugs). 🤘
— Sean Matheson (@controlplusb) October 30, 2017
First time of using @wallabyjs all day long at my professional work. Just DOPE! Works like a charm w/TypeScript,ES6,Mocha,Sinon,Chai,Atom.io
— Jens Krause (@sectore) September 2, 2015
If you're a JavaScript dev, you have to check out @wallabyjs, you will not be disappointed, put your dev workflow on steroids.
— Wesley Higbee (@g0t4) August 19, 2015
I just did a decently complex refactor on my JS app — and using wallaby.js made it 10x faster.
— Bryan Mills (@diffkid) August 12, 2015
Just started using @wallabyjs for the first time in a js based web project and it is incredible!!!
— Mob Mentality Show (@mob__mentality) June 30, 2021
The test, error, and log feedback is instantaneous just like @remcomulder's NCrunch.
Development productivity in our #mobProgramming skyrocketed today🚀
-Austin
That moment you realise you've forgotten to start @wallabyjs and you've been wasting your time by manually running your unit tests.
— Rich Somerfield (@richie5um) November 18, 2016
WOW.. 1 minute into @wallabyjs and I'm reeaaally impressed. Now for some Babel ES6/7 preprocessing
— Einar Ingebrigtsen (@EinarI) June 18, 2015
Man, @wallabyjs is a great test runner. Good support too. 2 hours from initial bug report to them pushing a fix live. :)
— Cody Hatch (@Codayus) June 17, 2015
Huge thank you to @AngularDutch and @wallabyjs for the Wallaby license! Gave it a spin, it's both so awesome and useful to see test status & info directly in-line, as you code. And the integrated output is also extremely helpful 🥳
— Marian Stoica (@MrnStoica) December 2, 2020
Billion might be pushing it but @wallabyjs is a nice player in the commercial extension space to watch out for.
— Peter Cooper (@peterc) December 3, 2020
Been messing around with the @wallabyjs license I won at last week's @AngularDutch meetup and I have to say I'm quite impressed by it. It might even make me pick up @code more often, maybe Vim integration someday? Thanks, folks! Looking forward to tonight's meetup.
— Joris Kraak (@joriskraak) December 17, 2020