Learn Grunt, Jest and Ruby

jest

Jest is a fast and safe testing framework with a focus on simplicity. 
This lesson will walk you through how to add jest to your application by running `yarn add --dev jest` followed by updating your `package.json` to be able to run your tests on the console by using the `yarn test` script.
This lesson covers how to create your first test by creating your first block that groups several related tests with `describe` and then adding your first test method using either the `it` or `test` keyword.

Add Jest to Your Application and Create Your First Test

The pluggable linting utility for JavaScript and JSX.

eslint

We can leverage GitHub Actions to automate the running of all of our accessibility auditing tools as part of a Continuous Integration (CI) workflow. 

Auditing tools will only catch a percentage of potential accessibility issues, it is no replacement for manual testing.  But being able to automate the auditing will add efficiencies to our testing and provide an early warning system that can be run much more frequently than it’s practical to perform manual testing.  Additionally, we can use our CI suite as a safety net to prevent code changes that break accessibility from being able to be merged.

## Resources
* https://app.egghead.io/lessons/react-set-up-eslint-to-audit-accessibility-issues-in-react
* https://docs.cypress.io/guides/continuous-integration/github-actions#Basic-Setup
* https://github.com/cypress-io/github-action

Automate Accessibility Audits with GitHub Actions

React is one of the web’s most popular frameworks for building JavaScript applications. 

If you know what you’re doing, React can drastically simplify how you build, use, and maintain code.

Whether you’re a React newbie or you’re ready for advanced techniques, you can level-up with egghead. Explore our in-depth courses, lessons, and community resources to build more powerful applications and crack open your career.

react

We can add accessibility testing to our `jest` unit tests with `jest-axe` which gives us:

* An easy way to automate accessibility auditing
* the flexibility to audit at any level of our code, as low as an element and as high as a component representing an entire page of our app
* A safety net for any accessibility regressions

Here we'll see how to use `jest-axe` with `react-testing-library` to render the components for `jest-axe` to audit for accessibility.

The React Testing Library is a very light-weight solution for testing React components. It provides light utility functions on top of react-dom and react-dom/test-utils, in a way that encourages better testing practices.

## Resources
* jest-axe: https://github.com/nickcolley/jest-axe
* react-testing-library: https://testing-library.com/docs/react-testing-library/intro/

Write Better Unit Tests with react-testing-library and jest-axe

We can add accessibility testing to our `jest` unit tests with `jest-axe` which gives us:

* An easy way to automate accessibility auditing.
* The flexibility to audit at any level of our code, as low as an element and as high as a component representing an entire page of our app.
* A safety net for any accessibility regressions.

Here we'll see how to use `jest-axe` with `enzyme` to render the components for `jest-axe` to audit for accessibility.

Enzyme is a JavaScript Testing utility for React that makes it easier to test your React Components' output. You can also manipulate, traverse, and in some ways simulate runtime given the output.

## Resources
* jest-axe: https://github.com/nickcolley/jest-axe
* enzyme: https://enzymejs.github.io/enzyme

Write Unit Tests for Accessibility Using jest-axe and enzyme

We can add accessibility testing to our `jest` unit tests with `jest-axe` which gives us:

* An easy way to automate accessibility auditing.
* The flexibility to audit at any level of our code, as low as an element and as high as a component representing an entire page of our app.
* A safety net for any accessibility regressions.

Here we'll see how to use `jest-axe` with `ReactDOM` to render components for `jest-axe` to audit for accessibility.

## Resources
* https://github.com/nickcolley/jest-axe

Render Components with ReactDOM to Write Tests with Jest and jest-axe

Best practices for building & testing redux applications have changed dramatically over time. This course aims to be a comprehensive yet understandable resource for those seeking to improve the testing of their redux applications.

This course is broken up into three parts.

The intro is look at how to add jest to an existing react redux application that was built on top of [vite](https://vitejs.dev/). We cover basic functionality like [watch mode](https://jestjs.io/docs/cli#--watch) and generating and using [code coverage](https://jestjs.io/docs/cli#--coverageboolean) to inform our testing strategy.

The first section covers the specifics of unit testing the redux code in our application. We'll go over how to test reducers, selectors and thunks. As part of this we'll touch on mocking APIs and using [Redux Mock Store](https://github.com/reduxjs/redux-mock-store) as well as running actions through our applications' actual reducers to broaden our test coverage.

Finally we'll look at how we can test our redux connected react components using the various utilities that come with the [React Testing Library](https://testing-library.com/docs/react-testing-library/intro/). We'll cover simulating various kinds of user input with the [user-event module](https://testing-library.com/docs/ecosystem-user-event), populating our redux store with test data, using [jest spy](https://jestjs.io/docs/jest-object#jestspyonobject-methodname), how to wait for asynchronous tasks to complete, and several approaches for finding & asserting that visual elements exist on the page.

This course is built on top of content that was created for the [Modern Redux with RTK and TypeScript](https://app.egghead.io/playlists/modern-redux-with-redux-toolkit-rtk-and-typescript-64f243c8) course and I highly recommend you start there if you haven't completed it already. 

I'm confident you will level up your redux testing abilities if  watch these lessons and practice coding each of them as you go.

Intro to Confidently Testing Redux Applications with Jest & TypeScript

Intermission Pep Talk - Testing Redux Applications

The [reselect module](https://github.com/reduxjs/reselect) popularized a pattern of memoized redux selectors. Now that pattern is baked into Redux Toolkit with its [createSelector](https://redux-toolkit.js.org/api/createSelector) method, which is used by the `getMemoizedNumItems` selector we're testing here.

Any selectors created with `createSelector` come with these two additional methods `recomputations()` and `resetRecomputations()`. These methods keep track of how many teams your data was recomputed and are essential for testing these selectors.

Some additional examples on testing memoized selectors can be found here:
https://github.com/reduxjs/reselect#q-how-do-i-test-a-selector



----

The createSelector method first takes any number of "input selectors" which gather data from your redux store and then for its final arguments takes an additional selector which has for its inputs the result of those input selectors.

The memoization is broken if either the initial state is unchanged OR if the any of the  results of the input selectors are unchanged. It uses `===` equality and not any sort of nested equality checking so `state` and `{ ...state }` would not be considered the same and always would recompute. On the flip side passing in `state` and then running `state.count++` would not trigger a recompute automatically, because the `state` object reference has not changed and `===` would pass. It definitely tripped me up a few times, so keep an eye out for issues with this.




Unit Testing a Memoized Redux Selector Built with Reselect/RTK

Redux is a predictable state container for JavaScript apps.
It helps you write applications that behave consistently, run in different environments (client, server, and native), and are easy to test.

redux

There are several ways to mock APIs for our tests.

Here we're using [jest.mock](https://jestjs.io/docs/es6-class-mocks#calling-jestmock-with-the-module-factory-parameter) with the module factory parameter to a new mocked module to replace our original. This helps us avoid problems like servers taking a long time and node.js not having fetch built-in.

When using mocks this way it's important to note that this mocked module is only going to show up for the tests executed in this file. Other test suites will continue to receive the original implementation of app/api. 

Other approaches to mock APIs include mocking out `window.fetch` or using [Mock Service Worker](https://mswjs.io/docs/getting-started/integrate/node) to provide a more robust API implementation. However, the approach we took here makes sense for our use case. We have a simple API surface, it lives in a single file, we never call `fetch` directly and we don't need a lot of bells and whistles (like responding to different routes or query parameters). So for that reason this approach and the [spyOn](https://jestjs.io/docs/jest-object#jestspyonobject-methodname) approach used in some of the later lessons actually works really well.

If you're using [Apollo](https://www.apollographql.com/) or [ReactQuery](https://react-query.tanstack.com/) or [SWR](https://swr.vercel.app/) to handle your data, then you almost certainly should use [Mock Service Worker](https://mswjs.io/docs/getting-started/integrate/node) instead of the jest.mock approach.

Mocking out our API Helper with jest.mock

Code coverage is an important part of any test setup. One of the jest framework's innovations is built-in test coverage support. In this lesson I demonstrate using the [collectCoverageFrom](https://jestjs.io/docs/configuration#collectcoveragefrom-array) configuration option to improve jest's coverage support for TypeScript files and then demonstrate using `npx jest --coverage` to run code coverage as well as `npm test -- --coverage`, which does the same thing.

At the end I briefly mention the [collectCoverage](https://jestjs.io/docs/configuration#collectcoverage-boolean) flag which seems like you'd want to always just have on, but in practice is annoying. That's because coverage takes several extra to process and I rarely need my code coverage run, so it just makes the testing feedback loop a lot slower. For a build-only config it might make sense to leave on.

----

There's a [pretty good question on stackoverflow](https://stackoverflow.com/questions/43046885/what-does-do-when-running-an-npm-command) that covers using `--` with `npm test` that you might want to check out.

Here's an explanation of [how npx differs from npm](https://medium.com/@maybekatz/introducing-npx-an-npm-package-runner-55f7d4bd282b).


Configuring Code Coverage for TypeScript Files in Jest

Jest has a [watch mode](https://jestjs.io/docs/cli) that can really speed up test development. It will automatically run your tests as you save your test files. And it has a built-in pattern option to allow you to only focus on tests for a particular file. This approach works well in combination with [test.todo](https://jestjs.io/blog/2019/01/25/jest-24-refreshing-polished-typescript-friendly#testtodo) where you can stub out a number of tests and then code on them until they all pass.

Most of what is being done in these tests we've already seen before and it's important to note that I'm doing only the most basic of testing here. For each of these actions it wouldn't be uncommon in production to have 3-6 tests instead of just one.

It's important to note that `it` and `test` are aliases of one another so `it.todo` and `test.todo` both work seamlessly and are just a matter of preference. *Usually* when I'm doing unit testing I'll stick with `describe` and `it`, which commonly go together and I use `test` without `describe` when I'm testing react components with [React Testing Library](https://testing-library.com/docs/react-testing-library/intro).

Using Jest in Watch Mode with test.todo to Test a Redux Reducer

The app is built on top of [vite](https://vitejs.dev/) instead of the more popular [create react app](https://reactjs.org/docs/create-a-new-react-app.html). The benefit of vite is that it installs and builds extremely quickly. One of the downsides of vite is that it doesn't come with any out-of-the-box testing support. It also has its own [esbuild-based compiler](https://vitejs.dev/guide/features.html#typescript), which is not currently compatible with jest, so we have to configure JSX & TypeScript support for jest even though `vite` handles that already for our app.

This lesson requires installing a handful of modules:
```
npm install -D jest
npm install -D @testing-library/react @testing-library/jest-dom @testing-library/user-event
npm install -D @babel/preset-react @babel/preset-typescript @babel/preset-env
npm install -D identity-obj-proxy
```

Each of them serves an important purpose:

- [jest](https://jestjs.io/) _runs our tests_
- [@testing-library/react](https://testing-library.com/docs/react-testing-library/intro) adds the ability to render react components inside of our test environment
- [@testing-library/jest-dom](https://github.com/testing-library/jest-dom) _allows us to assert that components are in the DOM and contains certain text and classes_
- [@testing-library/user-event](https://testing-library.com/docs/ecosystem-user-event) _allows us to interact with rendered components programmatically_
- [@babel/preset-react](https://babeljs.io/docs/en/babel-preset-react), [@babel/preset-typescript](https://babeljs.io/docs/en/babel-preset-typescript), and [@babel/preset-env](https://babeljs.io/docs/en/babel-preset-env) allow us to use ES6 Modules, JSX, and TypeScript in our tests
- [identity-obj-proxy](https://github.com/keyz/identity-obj-proxy#identity-obj-proxy---) is helpful when rendering CSS modules so that we can see the original class names instead of obfuscated ones

We also have to add numerous config files such as `babel.config.js` and `jest-setup.ts` which are required to enable all of this functionality.

We put our `jest` config in our `package.json` file which works well, but you can also put it in a file named `jest.config.ts` or `jest.config.js`. See the [Jest Configuration Documentation](https://jestjs.io/docs/configuration) for more details about configuring jest.



Adding Jest with TypeScript Support to a Vite Application

In this lesson we go after the elusive goal of 100% test coverage by testing a few additional cases: error responses, empty error messages and the pending state that should exist between checkout being clicked and the API returning data.

The first two require special handling in our mock API:

```typescript
if (items.evilItem > 0) throw new Error();
if (items.badItem > 0) return { success: false };
```

In some ways these are arbitrary examples that may not exist in your other applications, but I wanted to demonstrate the fact that there are a lot of different ways an API might decide to communicate errors.

In general with AJAX calls a non-200 status response often gets thrown as an error and treated as an error case, but some APIs (such as graphql) include errors as part of a normal `200` response and need special handling. These lessons are meant to demonstrate what that might look like in your mocks.

Now it's useful to reiterate here that our simple API interface makes writing these mocks very easy, but in many cases something like [Mock Service Worker](https://mswjs.io/docs/getting-started/integrate/node) is a more appropriate way to mock out an API.

For our "pending" test, it's interesting what we lose when we stop focusing on actions fired (like in our previous 2 lessons) and instead focus purely on the resulting state. It makes looking at the intermediary state a bit more difficult. Here we work around that by calling `store.dispatch(thunk)` and saving the results of that to an `action` variable, which we `await` after doing an initial assertion. That `await` triggers our mock API to respond, so we can use the space between `dispatch` and `await` to peak into the pending state.

Additional Redux Thunk Unit Tests for Increased Code Coverage

In a lot of ways plain selectors like we're testing here are extremely simple to reason about. The only thing that's a little tricky is even though they're often written side-by-side with a reducer, they accept the `RootState` instead of the reducer state. When writing these tests with TypeScript you often find yourself using `as` to cast partial state into full `RootState` type.

Here we're doubly nesting our `describe` blocks and it works great and makes our test output nicely formatted.

Unit Testing a Basic Redux Selector

For this lesson we focus on running our thunks through our app's reducer methods to test both the thunks and the reducers in a single test. Testing our thunks this way gives us more confidence they are working exactly as we expect and its less code for us to write. The main challenge we face in using our redux store this way is that we need to preload it with state.

To make that simpler we create two helper utilities: `getStoreWithState()` and `getStateWithItems()`. We're going to continue to use these utilities throughout our lessons. 

You'll notice I keep referring to the generated store as our "real redux store", even though we aren't relying on the `store` variable but generating a new store with the same reducers. What I really mean here is that our store has the same middleware and reducers as our app's store. Generating a new store for each test is important so that they can have their own state that don't conflict with other tests.

**Note**: It's also possible to generate the app's `store` variable with `getStoreWithState()`, but it makes the TypeScript syntax more complex and it seemed like it wouldn't add a lot of value.

Unit Testing Redux Thunks and Associated Reducer Methods using Your App's Redux Store

[Redux Mock Store](https://github.com/reduxjs/redux-mock-store) is a library that provides two important capabilities. 1. It makes it easy to pre-load state. 2. It keeps track of which actions were fired. We take advantage of both here for testing our thunk, in what amounts to just a slightly cleaner approach than using `jest.fn()` as we did in our previous lesson.

[Redux Mock Store](https://github.com/reduxjs/redux-mock-store) is more commonly used as a way to test redux-connected components, but also works anytime we need an easy way to confirm that certain actions are fired into our redux store.


While it does make it easy to populate a redux store and inspect which actions were fired, redux mock store doesn't have any reducers, so you can't use it in tests where you want your components to update in response to any actions. It's strictly a read-only store. Another challenge of using redux mock store is that it needs to be configured separately from your primary redux store. There may be cases where you'll have a middleware on your production redux store, but forget to add it to your mock store, leading to tests that don't match the behavior of your application. For these reasons I think it's generally better run both unit and integration tests against a store with your actual reducers hooked up when at all possible.

Unit Testing Redux Thunks using Redux Mock Store

The [reselect module](https://github.com/reduxjs/reselect) popularized a pattern of memoized redux selectors. Now that pattern is baked into Redux Toolkit with its [createSelector](https://redux-toolkit.js.org/api/createSelector) method, which is used by the `getTotalPrice` selector we're testing here.

Any selectors created with `createSelector` come with these two additional methods `recomputations()` and `resetRecomputations()`. These methods keep track of how many times your selector was recomputed and are essential for testing.

The createSelector method first takes any number of "input selectors" which gather data from your redux store and then for its final arguments takes an additional selector which has for its inputs the result of those input selectors.

A cached response will be used, if one exists, when either the root state passed in to the selector is unchanged or if any of the results of the input selectors remain unchanged between calls. It uses `===` equality and not any sort of nested equality checking so `state` and `{ ...state }` would not be considered the same and would always recompute. On the flip side passing in `state` and then running `state.count++` would not trigger a recompute automatically, because the `state` object reference has not changed and `===` would remain true. Writing tests for my memoized selectors definitely helped me better understand this behavior.

Some additional examples on testing memoized selectors can be found here:
https://github.com/reduxjs/reselect#q-how-do-i-test-a-selector




Unit Testing a Memoized Selector that Derives Data from Multiple Reducers

How to properly test thunks seems to be the source of a lot of confusion. Usually an API needs to be mocked and then there are numerous ways to actually run the tests. This lesson showcases the most basic approach which relies on [jest mock functions](https://jestjs.io/docs/mock-functions) and avoids hitting a redux store or reducer. 

For this lesson we're testing a thunk created using Redux Toolkit's [createAsyncThunk](https://redux-toolkit.js.org/api/createAsyncThunk) method. The test should continue work completely untouched even if we build the thunk by hand.

The [mock property](https://jestjs.io/docs/mock-functions#mock-property) of the `jest.fn()` we create here for our mock dispatch ends up doing most of the work. The nested array inside of the `calls` property measuring first "times called" and then "arguments passed" is a little bit confusing, but extremely powerful!

My least favorite part of this was needing to pass the third `extra` argument to our thunk to satisfy TypeScript. The other frustrating part was having to build a complete `RootState` object to pass into our `getState` method. We'll solve that in a later lesson by creating a `getStateWithItems` helper.

Unit Testing Redux Thunks with a Mock Dispatch Function

JavaScript® (often shortened to JS) is a lightweight, interpreted, object-oriented language with first-class functions, most known as the scripting language for Web pages, but used in many non-browser environments as well such as node.js or Apache CouchDB. It is a prototype-based, multi-paradigm scripting language that is dynamic, and supports object-oriented, imperative, and functional programming styles.

javascript

One of the strengths of [Nx](https://nx.dev) is that it provides you easy access to some of the best tooling available. As such, whenever you generate a new app or lib inside an Nx workspace, it automatically preconfigures Jest for you and even sets up some pre-generated tests.

Run Jest tests for a React app with Nx

Rails is a web-application framework that includes everything needed to create database-backed web applications according to the Model-View-Controller (MVC) pattern.

rails

If you make a mistake when naming your database column, and have data that you want to keep unchanged. You can use the change method with the rename_column definition in your migrations files to update a single column name in your database.

Rename A Database Column with Ruby on Rails Active Record Migrations

If you're not careful you can write a test that's worse than having not tests at all. In this lesson we'll learn why that is and how you can avoid it by making sure your test can fail.

This is based on my blog post: [Make Your Test Fail](https://kentcdodds.com/blog/make-your-test-fail)

Make Your Test Fail

Hey Everyone 👋,

John Lindquist here with the second issue of AI Dev Essentials! It's been another busy week in the AI tooling world. The biggest splash was probably GPT-4.1 hitting the streets, but there's plenty more action around MCP, Vercel's v0, Google's developer tools, and interesting community discussions. I've spent some time with GPT-4.1 already (specifically in Cursor), and while it shows promise, it didn't quite convince me to switch from Gemini 2.5 Pro yet. It stumbled on a few basic requests where Gemini usually shines on the first attempt.

---

### New egghead.io Lesson This Week:

* **[Create a Custom MCP that Calls Cursor Tools](https://egghead.io/create-a-custom-mcp-that-calls-cursor-tools~r77sw):** Learn how to build custom MCP server tools that allow Cursor's AI Agent to access your local project context. This lesson shows how to use Zod schemas and the crucial `.describe()` method to explicitly request information (like Git status or version) from the Cursor environment *before* your tool runs, enabling powerful, context-aware automation.

---

Here are the highlights that caught my eye this past week.

## Model Mania: GPT-4.1 Arrives, Plus Grok & Llama Updates

* **GPT-4.1 Lands:** OpenAI announced GPT-4.1, and it quickly became available via the [API](https://openai.com/live/) and showed up in [Cursor](https://x.com/cursor_ai/status/1911835651810738406). Cursor is offering it free for now to let users get a feel for it, though they don't recommend it as a default just yet. Curious to hear initial impressions from folks testing it out for coding tasks.

* **Grok 3 in Cursor:** Following other model additions, [Cursor also enabled Grok 3 models](https://x.com/amanrsanger/status/1910434915419906141), with the mini version available for free users. Aman Sanger noted it seems to "think upfront more than other models."

* **Community Hack: Llama 4.0 via Groq in Cursor:** Levi Dan shared a [detailed (and slightly hacky) guide](https://x.com/lxvi_brg/status/1908865544721154455) on how to wire up Groq's fast Llama 4.0 API into Cursor by using the OpenAI API key slot and intercepting requests. A clever workaround for the adventurous!

## Tooling & Platform Pulse

Lots of movement across different platforms and tools this week:

* **Vercel Ecosystem:**

  * Guillermo Rauch teased [v0 coming to VS Code](https://x.com/rauchg/status/1911524154458984515), hinting at tighter integration for the UI generation tool.

  * v0 also [added AI integrations](https://x.com/v0/status/1911912183149256943) with models from xai (Grok), FAL, Groq, and DeepInfra, including automatic API key setup and pay-as-you-go billing via Vercel Marketplace. They're offering a $10 credit for the Grok free tier.

  * Vercel shared insights on the [grep.app migration from CRA to Next.js](http://grep.app/), showcasing performance improvements. ([Source](https://x.com/rauchg/status/1911920410020757881)) I'm personally excited about this one – I rely heavily on examples when working with AI, and for me, a good example is often worth ten prompts. Tools like `grep.app` that make code discovery easier are invaluable.

* **Google's Growing Stack:**

  * Project IDX has officially become [Firebase Studio](https://x.com/_davideast/status/1909990728593453455), positioning itself as a cloud-based, agentic dev environment for full-stack AI apps, deeply integrated with Firebase. I've tried spinning up a few sites with it, and the speed is impressive. However, for more complex tasks like designing from images or intricate interactions, I still find myself leaning towards v0 for now.

  * Google quietly released the [Agent Development Kit (ADK)](https://x.com/omarsar0/status/1910004370864742757), a Python library (`pip install google-adk`) for building multi-agent systems with features like state management, tool usage, and orchestration. I haven't had a chance to dive into this yet, but it's right at the top of my list. Building robust agent systems is a huge area of interest, so this is probably the announcement I'm most excited about exploring this week.

  * Ramón Medrano Llamas shared his experience [moving back to VS Code from Cursor](https://x.com/rmedranollamas/status/1909516749612999149), highlighting the effectiveness of GitHub Copilot combined with the Gemini Code Assist extension (using Gemini 2.5 Pro in Agent Mode). I gave the Gemini Code Assist extension a try myself, but as someone deeply embedded in the Cursor workflow with established keyboard shortcuts and patterns, I struggled to find a flow I liked and didn't stick with it for long. It's interesting to see different perspectives, though!

  * AI features are rolling out more broadly in [Chrome](https://x.com/iam_chonchol/status/1909942954686636224), including text grabbing from YouTube videos and Google Lens integration.

* **Cloudflare Corner:**

  * Big news for edge compute: [Cloudflare Containers are coming to Open Beta in June](https://x.com/CherryJimbo/status/1910682562499850405), enabling running containerized apps (Next.js, Go, PHP confirmed) directly on the edge. This is huge news, in my opinion. Think about all the WordPress sites and other applications that rely on containerization. Opening this up on the edge unlocks incredible possibilities, including for AI applications. I'm super hyped to see what people build with this come June.

  * A new tool, [MCPify.ai](http://mcpify.ai/), launched for building MCP servers conversationally, built entirely on Cloudflare Workers and Durable Objects. ([Source](https://x.com/pbteja1998/status/1911723180445610149))

  * Securing MCP servers is getting easier, with examples shared using [WorkOS AuthKit](https://x.com/WorkOS/status/1910722639036874943) and [Auth0](https://x.com/dschenkelman/status/1910693265566728319).

* **IDE Updates:**

  * JetBrains shared the public [WebStorm roadmap for March-April](https://youtrack.jetbrains.com/issue/WEB-72310). ([Source](https://x.com/WebStormIDE/status/1909291367504748937))

> **✨ Workshop Spotlight: Conquer the Complexity of Cursor (Europe Friendly Time!) ✨**
>
> Missed the last workshop or found the timing tricky? This one's for you! Master practical AI development workflows in Cursor in a session scheduled for **12:00 PM UTC** to better accommodate European attendees.
>
> This hands-on workshop covers Agents, Ask, Custom Modes, multi-file analysis, effective prompting, Cursor rules, and strategies for handling AI failures. Unlock Cursor's potential and streamline your development process.
>
> * **When:** \[Check website for upcoming dates - This session is Europe-friendly at 12:00 PM UTC\]
>
> * **Where:** Zoom (Live Q&A included)
>
> * **Investment:** $149
>
> ➡️ [**Read More about the Workshop**](https://egghead.io/workshop/cursor)
> ➡️ [**Register Now ($149)**](https://buy.stripe.com/7sI7tT81dfpC06s28c)
>
> *(Team training also available)*

## Community Buzz & Resources

* **MCP Explained:** Kent C. Dodds wrote a piece explaining [why he's excited about Model Context Protocol (MCP)](https://www.epicai.pro/the-game-changing-potential-of-model-context-protocol) and its potential. ([Source](https://x.com/kentcdodds/status/1911840456432034112))

* **Prompting Guide:** Ian Nuttall surfaced [v7 of Google's Prompt Engineering Guide](https://x.com/iannuttall/status/1911086164196606314), a deep dive into techniques and best practices. Definitely worth a look.

* **Discussion Starter:** Eric Zakariasson asked the community about their [favorite CLIs and MCP servers to use with the Cursor agent](https://x.com/ericzakariasson/status/1910808935961088346). What are you all using?

* **Gemini 2.5 Pro Praise:** The positive buzz around Gemini 2.5 Pro continues to grow in the community. It's getting rave reviews and even achieving 'S-tier' status on social platforms like Reddit for its coding capabilities. ([Source](https://x.com/suchenzang/status/1911251230317490416))

That’s a wrap for this week! There's always so much happening, it's hard to keep up, but hopefully, this helps surface some of the more interesting bits for developers working with AI.

If you have any feedback or questions, feel free to respond to this email. Always happy to talk shop about the latest AI tools.

John Lindquist

[egghead.io](https://egghead.io)

John Lindquist

AI Dev Essentials #2: GPT-4.1 Arrives, MCP Deep Dive & Google's Agent Dev Kit

AI Dev Essentials #2: GPT-4.1 & Gemini updates, MCP tools, Vercel v0, Google ADK, Cloudflare Containers news. Latest AI dev tooling highlights.

In this quick walkthrough, you’ll learn how to drop Nx into an existing npm or pnpm workspace and immediately benefit from project graph visualization, caching, and smart task orchestration, all without rewriting your setup.

You’ll start with a standard React monorepo containing a Vite app, a UI package, and utility functions. Then, using a single command (`nx init`), you’ll initialize Nx and see how it auto-detects your existing scripts, builds a dependency graph, and enables advanced features like affected commands and local caching.

We're also going to explore optional enhancements using Nx plugins for Vite and React. You’ll see how they help Nx infer tasks directly from your Vite config files, improve DX with the Nx Console VS Code extension, and leverage Nx plugin generators to scaffold code with a consistent structure.

What you’ll learn
- How to initialize Nx in an existing npm or pnpm monorepo
- How Nx understands your workspace structure and scripts
- How local caching and affected builds speed up development
- How optional Nx plugins improve DX without adding bloat
- How to scaffold new packages

Using Nx on an existing React and NPM workspace based monorepo

Applying Nx to an existing React monorepo to enable caching, task orchestration, and project graph analysis without changing your current setup.

Typing repetitive or complex instructions for Cursor's AI agent can slow down your workflow. This lesson teaches you how to create custom slash commands (e.g., `/s term`, `/l`, `/c`) using Cursor's "Rules" feature. Learn how to map these simple shortcuts to specific AI actions, instructing the agent to use precise tools like `codebase_search`, `edit_file`, or `run_terminal_cmd` based on your command and the current conversation context.

**Workflow demonstrated in this lesson:**

*   List available AI tools (built-in and MCP) to get their exact names.
*   Navigate to Cursor Settings -> Rules.
*   Define custom rules under a heading (e.g., `## Slash Commands`).
*   Create rules mapping a slash command pattern (like `/s <term>`) to a detailed instruction specifying which tool to use and how (e.g., "Use the codebase_search tool to search for <term/>").
*   Define rules that leverage conversation context (e.g., for summarizing notes or creating commit messages).
*   Save the rules (potentially in `.cursor/rules/project.mdc` for team sharing).
*   Invoke the custom slash commands (e.g., `/s handle`, `/l`, `/c`) in the chat/agent window.
*   Observe the AI understanding the shortcut and executing the intended tool call.

**Key benefits:**

*   Creates efficient, reusable shortcuts for common AI interactions.
*   Reduces the need for typing lengthy, detailed prompts repeatedly.
*   Allows mapping simple commands to specific Cursor tool invocations.
*   Enables commands that leverage the ongoing conversation context.
*   Improves workflow speed and consistency when working with the AI agent.

Speed Up Your Agents with Cursor Slash Commands

Hey Everyone 👋,

John Lindquist here. Since I've been diving deep into AI tooling and workflows over the past year, I'm starting this weekly newsletter to share updates on what interests me and could be helpful to the community. The goal is to help everyone stay up-to-date with the latest in essentials tools for AI devs.

I'll focus on relevant community news, model evaluations for coding, notable tools like Cursor and Windsurf, and practical workflows (including tools I build myself 😇). This week kicks off Cloudflare Developer Week with major announcements around agent/MCP services that many of us will likely use soon (I'll dig in and share my thoughts next issue). There are also lots of hints about new coding models possibly coming to Cursor (though my preference remains Gemini 2.5). Personally, I'm hoping for a Gemini Flash 2.5 variant. So let's hop into the latest! For my detailed, up-to-date workflows, check out the workshop info below.

Recent egghead.io lessons about AI tooling:

* **[Swarm Intelligence: Massively Parallelize Your AI Agents in Cursor](https://egghead.io/swarm-intelligence-massively-parallelize-your-ai-agents-in-cursor~g7u2g):** A workflow using `file-forge`, AI scripting, and a custom `git worktree` tool (`wt`) to launch parallel Cursor agents on different branches.
* **[Build a Better Edit Tool in Cursor with Custom Agent Modes](https://egghead.io/build-a-better-edit-tool-in-cursor-with-custom-agent-modes~21rr0):** Create a focused 'edit mode' in Cursor for precise AI refactors without conversational overhead, overcoming Command-K limitations.
* **[Visually Clone Websites with Gemini 2.5 Canvas for Cursor](https://egghead.io/visually-clone-websites-with-gemini-2-5-canvas-for-cursor~s5ugk):** Use Gemini 2.5 Pro's Canvas feature within Cursor to analyze and replicate website structures.

---

## Cloudflare Developer Week: Agent & Platform Updates

Cloudflare announced several updates relevant to AI application development:

* **Durable Objects Free Tier:** Lowers the barrier for experimenting with stateful serverless and the Agents SDK. ([Rita Kozlov](https://x.com/ritakozlov_/status/1909231625855983939))
* **MCP Enhancements:** BYO Auth (incl. [Auth0](https://x.com/auth0/status/1909307220816228354)) and Hibernation for MCP servers aim to improve agent security and efficiency. Exercise caution with MCP, but these are steps toward production viability.
* **Workflows GA & autoRAG:** Orchestration tool is now GA; a new autoRAG product indicates more integrated AI solutions.
* **Outerbase Acquisition:** Expect Durable Objects usability improvements following this acquisition. ([Rita Kozlov](https://x.com/ritakozlov_/status/1909232149246492887))
* **OpenNext Adapter Beta:** v1.0-beta for deploying Next.js apps on Cloudflare Pages adds caching, PPR, middleware support. ([CloudflareDev](https://x.com/CloudflareDev/status/1909598450871652398))

**Summary:** Cloudflare is actively enhancing its platform for AI/agent development, particularly reducing friction with Durable Objects and MCP.

## Llama 4 & Nemotron-Ultra Released

Meta's Llama 4 models began rolling out, with initial reports of variable quality across implementations. Meta attributes this to implementation stabilization, denying training on test sets ([Ahmad Al-Dahle](https://x.com/Ahmad_Al_Dahle/status/1909302532306092107)). Nvidia subsequently released **Llama-Nemotron-Ultra** (253B parameters), derived from Llama-405B via pruning and reasoning-focused post-training. Open weights and data are available ([Oleksii Kuchaiev](https://x.com/kuchaev/status/1909444566379573646)).

**Summary:** More powerful open models are available. Llama 4's initial rollout highlights the importance of stable implementations. Nemotron-Ultra adds a high-end specialized option.

---

## Quasar Alpha: Stealth Model on OpenRouter

OpenRouter provides early access to "Quasar Alpha," a model with limited public details but notable claims: 1M token context, benchmarks reportedly surpassing Claude 3.7 Sonnet, and >4x faster speeds. Reports suggest strong coding performance comparable to O3 Mini/DeepSeek R1 but significantly faster ([Matthew Berman's Thread](https://x.com/TheMattBerman/status/1908286423976886371)). The originating lab remains anonymous; speculation includes GPT-5, Claude 4, or Gemini 3.

**Summary:** The combination of large context, speed, and reported coding strength warrants attention for agentic workflows and large codebase analysis, despite benchmark caveats. Worth testing via OpenRouter if accessible.

---

**✨ Workshop Spotlight: Conquer the Complexity of Cursor ✨**

Master practical AI development workflows in Cursor. This hands-on workshop covers Agents, Ask, Custom Modes, multi-file analysis, effective prompting, Cursor rules, and strategies for handling AI failures.

* **When:** **This Thursday!** April 10, 2025, 9:00 AM - 2:00 PM (PDT)
* **Where:** Zoom (Live Q&A included)
* **Investment:** $149

Unlock Cursor's potential and streamline your development process.

➡️ [**Read More about the Workshop**](https://egghead.io/workshop/cursor)
➡️ [**Register Now ($149)**](https://buy.stripe.com/dR67tT4P17Xa8CYfZ1)

*(Team training also available)*

---

## Quick Links

* **Nightwhisper Buzz:** Highly-rated coding model "Nightwhisper" (rumored Gemini 2.5 variant?) left LMSys Arena; release may be imminent. ([ʟᴇɢɪᴛ Tweet](https://x.com/legit_api/status/1908264443827351913), [AiBattle Tweet](https://x.com/AiBattle_/status/1907519430961025476))
* **AI SDK Speech-to-Text:** Vercel AI SDK added a `transcribe` function. ([AI SDK Tweet](https://x.com/aisdk/status/1909603418639155460))
* **Gemini 2.5 Pro Updates:** Supports YouTube URLs as input in AI Studio (transcribe, summarize, analyze); reported improvements reducing stop issues/displaying thinking tokens. ([Jean Gatt Tweet](https://x.com/jean__gatt/status/1909256747518226829), [Eric Zakariasson Tweet](https://x.com/ericzakariasson/status/1908619515023548880))
* **Baby Cursor Project:** Cursor's Ryo Lu is building a rapid prototyping environment for IDE ideas. ([Ryo Lu Tweet](https://x.com/ryolu_/status/1908328050154233863))
* **(Rumor) Qwen3 Soon?:** Hints suggest Alibaba's Qwen3 model release is near. ([Elaina Tweet](https://x.com/Elaina43114880/status/1909572798944841859))

---

If you have any feedback or any questions, feel free to respond to this email. Always happy to talk shop about the latest AI tools.

John Lindquist

[egghead.io](https://egghead.io)

AI Dev Essentials #1: Cloudflare agent updates, Llama 4/Nemotron/Quasar models, Cursor workshop

Cursor's AI Agent has the abilitly to invoke MCP tools, but they lack direct access to your project. This lesson shows how to build custom MCP (Model Context Protocol) server tools that bridge this gap. Learn to define tool parameters using Zod schemas and the crucial `.describe()` method to explicitly request necessary context from the Cursor environment *before* your tool runs. See how the AI gathers this information (like Git status or version via terminal commands, or web search results) and passes it to your tool, enabling powerful, context-aware automation.

**Workflow demonstrated in this lesson:**

*   Scaffold a basic MCP server using a Cloudflare template (`pnpm create cloudflare`).
*   Run the MCP server locally and configure it in Cursor settings.
*   Define MCP tools (e.g., `status`) within the server code (`index.ts`).
*   Specify required context for tools using Zod schema parameters and `.describe()` (e.g., requesting "The status of the git repository").
*   Interact with the Cursor Agent using natural language (e.g., "Please check the status").
*   Observe the Agent's thought process: identifying the need for specific context based on the `.describe()` text.
*   See the Agent automatically using its *own* tools (like `run_terminal_cmd` or `web_search`) to gather the requested context *before* calling your MCP tool.
*   Watch the Agent call your MCP tool, passing the gathered local context (Git status, version, etc.) as arguments.
*   Receive the final response from the Agent, incorporating the information provided by your local MCP tool.

**Key benefits:**

*   Allows Cursor's AI to access and reason about information from your local machine (Git status, versions, file contents, etc.).
*   Enables the creation of AI tools that directly interact with or report on your local development environment.
*   Demonstrates the power of using `.describe()` in Zod schemas to guide the AI in gathering necessary context automatically.
*   Unlocks advanced automation possibilities by combining AI reasoning with local machine access.

Create a Custom MCP that Calls Cursor Tools

Vimium's Vomnibar is a "command palette"-like search tool for your open tabs, browser history, and bookmarks. We can search through and jump to any tab open across browser windows. We can also do a generalized search with results that also include browser history and bookmarks which can either be opened in the current tab or a new tab. If you're anything like me, you open tons of tabs and visit hundreds of webpages over the course of a week. The vomnibar puts all of that at your fingertips.

Josh Branchaud

Open Tabs, Browser History, and Bookmarks with the Vomnibar

Vimium's Vomnibar is a "command palette"-like search tool for your open tabs, browser history, and bookmarks.

Another aspect of Vimium's configurability is customizable key mappings. We can add new mappings and override existing ones. If there is a certain Vimium feature you want to make easier to trigger, adjust the key mapping to suit your needs.

Configure Custom Vimium Key Mappings

Another aspect of Vimium's configurability is customizable key mappings. We can add new mappings and override existing ones.

Many aspects of Vimium can be configured in order to bend the tool to your specific needs and use cases. We look at how to configure what sites turn off Vimium, the default search engine, link hint characters, and other basic settings. We also see how both insert mode and searching a visual selection work. Custom keymappings and custom search engines are covered in subsequent lessons.

Configure Basic Aspects of Vimium

Many aspects of Vimium can be configured in order to bend the tool to your specific needs and use cases.

Vimium's "marks" feature lets you mark positions in the current tab and across tabs. These are positional markers that you can jump back to. For instance, as you browse a huge page of documentation or a massive forum discussion, you can leave a series of "dog ears" to sections or conversations that you'll later want to revisit. Each tab supports its own set of lower-case letter marks. Upper-case letter marks are shared across tabs allowing you to seamlessly move between a specific set of tabs regardless of how they are arranged.

Set Marks on a Vimium Webpage You Want to Jump Back To

Vimium's "marks" feature lets you mark positions in the current tab and across tabs. These are positional markers that you can jump back to.

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