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Building Confidence at the Boundaries: An Outside-In Testing Strategy

Presentation byEduardo AC

Modern JavaScript applications rarely fail because of a broken function. They fail at the boundaries: APIs, authentication, feature flags, browser APIs, payments and third-party services.

From a real journey at scale with over 1.3 million transactions, Eduardo will explore an outside-in testing strategy that focuses on what matters most: the interactions between your application and the outside world.

You’ll leave with practical techniques to build confidence, reduce brittle tests and ship changes with greater certainty, regardless of your JavaScript framework.

Presented at these Events
Cover Photo for JSMonthly London July Meetup #208
Thu, Jul 23rd · 5PMIn-Person

JSMonthly London July Meetup #208

Primary Photo for JavaScript Monthly London MeetupJavaScript Monthly London Meetup
Presented with these Guilds
Cover Photo for JavaScript Monthly London Meetup
Primary Photo for JavaScript Monthly London Meetup

JavaScript Monthly London Meetup

Javascript evolution has sped up (a lot) in recent years and event the most veterans developers find it hard to keep up with the latest trends. This meetup group aims to bring you monthly bite-sized updates on the world of Javascript along with a healthy dose of nice people, beer and pizza.

Please use your full name when registering, as some of our venues require a full list of attendees beforehand. You have an idea and you want to be a speaker?

We are always looking for more speakers - submit your talk here (https://docs.google.com/forms/d/e/1FAIpQLSdFaatfveOUbrmer47jYb5J4J4ttxAFc1CgTjUDltBXmDOJmg/viewform)

1.2KMembers
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API contracts are the backbone of modern frontend-backend collaboration, but manual integration slows teams down and increases errors. What if we could automate it? In this talk, we’ll dive into Shift Left API contract development and introduce an approach to automatically generate an NPM package from API contracts. This package provides: ✅ TypeScript types for strict FE & BE consistency ✅ Zod validation for safer forms and API responses ✅ Axios + React Query for streamlined fetching & caching ✅ Automated versioning & observability to ensure API integrity By shifting API validation, testing, and integration earlier in development, teams can move faster, reduce errors, and improve efficiency. Whether you're a developer, tech lead, or architect, this session will give you practical strategies to automate your API workflows and accelerate your development pipeline.
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Torc is a community-first platform bringing together remote-first software engineer and developer opportunities from across the globe. Join a network that’s all about connection, collaboration, and finding your next big move — together.

Join our community today!

Sponsor Logo for {0}

Don't let broken lines of code, busted API calls, and crashes ruin your app. Join the 4M developers and 90K organizations who consider Sentry “not bad” when it comes to application monitoring. Use code “guild” for 3 free months of the team plan.

https://sentry.io

Primary Photo for {0} {1}

Building Confidence at the Boundaries: An Outside-In Testing Strategy

Presentation byEduardo AC

Modern JavaScript applications rarely fail because of a broken function. They fail at the boundaries: APIs, authentication, feature flags, browser APIs, payments and third-party services.

From a real journey at scale with over 1.3 million transactions, Eduardo will explore an outside-in testing strategy that focuses on what matters most: the interactions between your application and the outside world.

You’ll leave with practical techniques to build confidence, reduce brittle tests and ship changes with greater certainty, regardless of your JavaScript framework.

Presented at these Events
Cover Photo for JSMonthly London July Meetup #208
Thu, Jul 23rd · 5PMIn-Person

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Primary Photo for JavaScript Monthly London MeetupJavaScript Monthly London Meetup
Presented with these Guilds
Cover Photo for JavaScript Monthly London Meetup
Primary Photo for JavaScript Monthly London Meetup

JavaScript Monthly London Meetup

Javascript evolution has sped up (a lot) in recent years and event the most veterans developers find it hard to keep up with the latest trends. This meetup group aims to bring you monthly bite-sized updates on the world of Javascript along with a healthy dose of nice people, beer and pizza.

Please use your full name when registering, as some of our venues require a full list of attendees beforehand. You have an idea and you want to be a speaker?

We are always looking for more speakers - submit your talk here (https://docs.google.com/forms/d/e/1FAIpQLSdFaatfveOUbrmer47jYb5J4J4ttxAFc1CgTjUDltBXmDOJmg/viewform)

1.2KMembers
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Cover Photo for Shifting Left with Automated API Clients

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API contracts are the backbone of modern frontend-backend collaboration, but manual integration slows teams down and increases errors. What if we could automate it?

In this talk, we’ll dive into Shift Left API contract development and introduce an approach to automatically generate an NPM package from API contracts. This package provides:
✅ TypeScript types for strict FE & BE consistency
✅ Zod validation for safer forms and API responses
✅ Axios + React Query for streamlined fetching & caching
✅ Automated versioning & observability to ensure API integrity

By shifting API validation, testing, and integration earlier in development, teams can move faster, reduce errors, and improve efficiency. Whether you're a developer, tech lead, or architect, this session will give you practical strategies to automate your API workflows and accelerate your development pipeline.

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Cover Photo for Testing our way to a better developer experience

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Are tests a chore, or do they help us move faster? Let’s examine what makes testing great and not so great. We’ll focus on test strategies that help us code with confidence and clarity, and where they can cost us time and energy. The secret to good testing lies in how it shapes our developer experience. Do our tests give us useful feedback in a timely manner? How quickly can we tell what is wrong when a test suite fails? Do they document our features and explain our past decisions? We’ll answer these questions with better tests that give us joy.

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Cover Photo for From Unit to E2Es — A Testing Guide to Sleeping Better at Night

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We all want to sleep well at night and be fully confident in the code we built. One thing that can contribute to increasing your number of hours slept is testing. This workshop will focus specifically on testing practices and patterns. In this session, we will go over the full testing spectrum from unit to e2e by understanding the tools for each specific case and how to use them. We will review some production stories and popular use cases and, by the end, learn how to build a testing suite to which even your product owners can contribute. 

Here are some of the tools you can expect to learn and use at this workshop:

React Testing Library: Let’s deep dive into how the library that made testing fun again works and how we can leverage it for writing unit and integrating tests. Mock Service Worker: Mocking is an essential part of testing, so let’s learn about one of the de facto libraries in the industry and use it to make mocking easier and faster. Vitest: we will learn why it is called the Next-generation testing framework and how we used it to double the speed at which our tests ran. Playwright: E2Es are an essential part of the testing pyramid. We will learn how Playwright works and enables us to write resilient tests. We will also learn about BDD and how to turn our user stories into automated tests.

By the end of this workshop, you should have a complete overview of the testing practices applied in production environments worldwide and be ready to take this knowledge with you and use it everywhere.

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API contracts are the backbone of modern frontend-backend collaboration, but manual integration slows teams down and increases errors. What if we could automate it? In this talk, we’ll dive into Shift Left API contract development and introduce an approach to automatically generate an NPM package from API contracts. This package provides: ✅ TypeScript types for strict FE & BE consistency ✅ Zod validation for safer forms and API responses ✅ Axios + React Query for streamlined fetching & caching ✅ Automated versioning & observability to ensure API integrity By shifting API validation, testing, and integration earlier in development, teams can move faster, reduce errors, and improve efficiency. Whether you're a developer, tech lead, or architect, this session will give you practical strategies to automate your API workflows and accelerate your development pipeline.
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Platform Sponsors

Sponsor Logo for {0}

Torc is a community-first platform bringing together remote-first software engineer and developer opportunities from across the globe. Join a network that’s all about connection, collaboration, and finding your next big move — together.

Join our community today!

Sponsor Logo for {0}

Don't let broken lines of code, busted API calls, and crashes ruin your app. Join the 4M developers and 90K organizations who consider Sentry “not bad” when it comes to application monitoring. Use code “guild” for 3 free months of the team plan.

https://sentry.io

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