What is E2E? A guide to end-to-end testing

For development teams, software testing is an essential practice that ensures the quality and functionality of applications before they reach end users. End-to-end testing, also known as E2E testing, is an approach to testing that that simulates real user experiences to validate the complete system.

This article will guide you through what E2E testing is, why it’s important, and how you can effectively implement it for your software projects.

What is end-to-end testing (E2E)?

E2E testing is a way to make sure that applications behave as expected and that the flow of data is maintained for all kinds of user tasks and processes. This type of testing approach starts from the end user’s perspective and simulates a real-world scenario.

Here’s an example. On a sign-up form, you can expect a user to perform one or more of these actions:

• Enter a blank email and password
• Enter a valid email and password
• Enter an invalid email and password
• Click a sign-up button

You can use end-to-end testing to verify that all these actions work as a user might expect.

In this case, the E2E testing framework would automatically enter data and interact with the sign-up button, just as a real user would. The test would then check responses from the application, such as ensuring that an error message appears when invalid data is entered or confirming a successful registration with valid data. It would also verify that all backend processes, like database updates and email notifications, occur correctly.

End-to-end testing may sound comprehensive, but it’s only one part of a good testing strategy. There are many other testing methods that you should combine with it to enhance overall software quality and reliability. Some other testing types you should consider include:

• Unit testing makes sure that every single component in a system works as expected
• Integration testing combines individual software modules and tests them as a group.
• Security testing evaluates the software for vulnerabilities and ensures that data is protected from external threats
• Accessibility testing ensures that the software is usable by people with a wide range of disabilities and complies with common accessibility standards
• Usability testing evaluates how user-friendly the application is, focusing on the ease with which users can complete tasks

These types of tests are different from end-to-end testing, which focuses on the complete user workflow.

Why is end-to-end testing important?

End-to-end testing has been widely adopted because it:

• Helps teams expand their test coverage by adding more detailed test cases than testing methods like unit and integration testing.
• Ensures correct application performance by running test cases based on the end user’s behavior.
• Helps release teams reduce the time to market by automating critical user paths.
• Reduces the cost of building and maintaining software by decreasing the time it takes to test it.
• Helps predictably and reliably to detect bugs before they are released to users.

End-to-end testing appeals to a cross-team group that includes developers, testers, managers, and users.

E2E benefits for developers and QA teams

For organizations that maintain a separate QA team, delegating E2E testing to the QA team frees devs to work on adding features to the application. Often it is easier for testers to write E2E tests because they are based on the user’s behavior, which can be observed during usability testing and documented in tickets.

E2E testing also works well in a DevOps environment, where automated testing is integrated into the developer’s day-to-day workflow. Using a continuous integration and continuous delivery (CI/CD) platform, E2E tests can be triggered any time the developer pushes changes to the main branch. If tests pass, updates deploy automatically; if they fail, developers are promptly notified to fix issues.

E2E benefits for managers

End-to-end testing provides managers with a clear understanding of how each part of the application interacts in real-world scenarios. This understanding helps when they prioritize the tasks that most directly impact user experience and system stability.

In this approach critical issues are addressed first, optimizing resource allocation and development efforts to improve product quality and customer satisfaction.

E2E benefits for users

End-to-end testing also improves the user experience, especially for applications requiring lots of user interaction, like web, desktop, and mobile apps.

Thorough E2E testing mimics real user interactions, helping to identify and resolve issues before they affect users. As a result, it leads to more reliable, intuitive, and user-friendly applications that meet or exceed user expectations.

E2E testing tools

End-to-end testing frameworks help developers implement comprehensive, automated test cases in just a few lines of code. Here are some of the most common ones:

• Playwright: Developed by Microsoft, Playwright has become a leading choice for E2E testing. It offers native support for Chromium, Firefox, and WebKit browsers, excellent parallel execution, and powerful debugging tools like trace viewer and codegen for recording tests. Playwright’s auto-waiting capabilities and modern API design make tests more reliable and easier to maintain.
• Cypress: Fast, user-friendly testing tool that runs directly in the browser. Cypress excels at component testing and visual debugging with its time-travel feature that lets you see exactly what happened at each step. It remains a strong choice for developer-centered testing workflows.
• Selenium: One of the most established tools for automating web browsers, Selenium supports multiple languages and frameworks. While newer tools have emerged, Selenium’s extensive ecosystem and language support keep it relevant for many teams.
• TestCafe: Node.js-based tool for testing in any browser that supports HTML5.
• Puppeteer: Developed by Google to test web pages on headless Chrome or Chromium over the DevTools protocol.
• Appium: Mobile-focused tool that allows E2E testing on both iOS and Android from the same API.
• Nightwatch: Integrated E2E testing solution for Node.js that uses the W3C WebDriver API to perform commands and assertions on DOM elements.
• BrowserStack: Cloud-based test tool that provides access to an extensive range of real mobile devices and browsers.

Many teams integrate these tools into their CI/CD pipelines to automate the execution of E2E tests. This automation ensures that tests are run consistently and reliably as part of the deployment process, helping to identify issues early and improve software quality continuously.

The trend in E2E testing frameworks is toward Playwright, which is now the top choice in many developer surveys. Teams migrating from older frameworks often cite Playwright’s speed, cross-browser WebKit support, and native parallelization as key benefits.

Challenges of end-to-end testing

End-to-end testing is a great way to test software, but it comes with some challenges too. Challenges present themselves because E2E testing:

• Is time-consuming
• Must be designed to reproduce real-world scenarios
• Requires a good understanding of user goals
• Demands ongoing maintenance as applications evolve

Time consuming

End-to-end testing can be time-consuming to set up because it takes a complete understanding of the product to write test cases. E2E tests can also be computationally expensive and slow to execute due to the complexity of simulating real user interactions across multiple components and systems.

While companies typically employ unit tests and integration tests throughout various stages of development, they strategically deploy E2E tests primarily for the most critical user workflows, running these tests in staging environments before final deployments. This minimizes the impact of slow-running tests during development while maintaining quality standards in production.

You can learn more about ways to optimize and effectively manage your testing strategies in The testing pyramid: Strategic software testing for Agile teams.

Difficult to design tests

Because E2E tests simulate the real-world behavior of users, there are many components to consider while designing these tests.

For example, you can run a web application on many browsers, and each browser has different specifications. This means you have to write tests that are specific to these browsers. This daunting task can lead to budget overruns. In test-driven development, where you’re looking for quick feedback on the code, relying exclusively on E2E tests isn’t a good approach.

Understanding user goals

Users aren’t looking for features: they just want to solve their specific problems. End-to-end testing should focus on how effectively the app solves its users’ issues.

The problem is that not all development teams have a detailed understanding of user intentions. So, they must deploy methods early on during software development to gather user perspectives and requirements. User research can be quite costly, so teams often rely on the same set of users to work as “beta testers” for an application.

Maintenance burden

As applications evolve, E2E tests require ongoing maintenance. A single UI change — like renaming a button ID — can break multiple tests. Building comprehensive E2E test coverage with traditional frameworks requires dedicated automation engineering teams, months of initial development, and ongoing maintenance that can consume the majority of testing effort.

Despite these challenges, E2E testing is still worth the investment because it provides the most comprehensive assessment of the software’s functionality in real-world scenarios. In the competitive world of software, the ability to both meet technical specifications and deliver a high-quality user experience can make or break a product’s success.

AI and the future of E2E testing

Artificial intelligence is transforming E2E testing, addressing many of the traditional challenges around time, complexity, and maintenance.

Agentic AI for testing

The rise of agentic AI has introduced autonomous agents capable of performing multi-step testing tasks. Rather than just asking an AI to “write a login test,” modern AI testing tools can:

• Scan a UI to identify changes automatically
• Update selectors in the test repository without manual intervention
• Run regression suites to verify the fix
• Flag code changes for human review

This shift from AI as a coding assistant to AI as an autonomous testing agent represents a significant evolution in how E2E testing can be used.

Self-healing tests

Flaky tests have always been a challenge in E2E testing. Self-healing automation is becoming a standard feature rather than a luxury add-on. Tools like CircleCI’s Chunk offer flaky test detection directly from your CI/CD pipeline. Many modern frameworks now incorporate:

• Dynamic wait times that automatically adjust timeouts based on application behavior
• Auto-retrying logic that intelligently retries failed assertions before marking tests as failed
• Adaptive selectors that can find a changed element (like a button ID) by text or accessibility role and flags the code change for later review

Playwright has championed many of these capabilities with its built-in auto-waiting features. The goal is tests that adapt to minor application changes without breaking, while still alerting teams to genuine issues.

Reduced maintenance burden

AI-powered testing tools are specifically targeting the maintenance burden that makes E2E testing expensive. By automatically detecting UI changes, suggesting test updates, and identifying redundant or obsolete tests, AI can significantly reduce the ongoing effort required to maintain a healthy test suite.

This allows QA teams and developers to focus on expanding coverage, optimizing test strategies, and high-value exploratory work rather than constantly fixing broken tests.

How to implement end-to-end testing

Now that you know that you want to add some E2E tests to your development process, where do you start? Designing the test cases is a good first step. Then, you can begin by testing manually until it makes sense to start automating your E2E tests.

Designing end-to-end test cases

Because E2E testing requires some preparation, it’s good to be familiar with the steps needed to implement them. Here are the steps for a typical E2E testing procedure:

1. Review the requirements to validate the E2E testing results
2. Set up test environments and requirements
3. Define all the processes of systems and subsystems
4. Describe the roles and responsibilities of each system and the subsystems
5. Outline the testing tools and frameworks
6. List the requirements for designing test cases
7. List the input and output data for each system

Once you have gone through these steps, you can implement E2E testing.

Manual end-to-end testing

Manual testing is performed by a human tester directly interacting with the testing software. These testers can quickly learn what works and what doesn’t when writing a test plan.

Manual testing helps identify test cases and hidden user interaction paths in the system. That gives testers the information they need to start automating test cases in the future.

There are two ways to do manual testing: horizontal and vertical.

• Horizontal E2E testing covers the entire application. It requires software development teams to have well-defined workflows and established test environments. A single test workflow can span multiple subsystems. A plan for simultaneously testing a UI, database, and email integration is an example of a horizontal E2E test.
• Vertical E2E testing breaks down the application into layers that you can test individually. Vertical E2E tests often precede their horizontal counterparts because of this granularity. For example, performing a vertical E2E test with user interface subsystems allows you to easily identify and fix bugs.

Automated end-to-end testing

As your project grows, manual E2E testing will become less manageable. This is especially true of testing user interfaces, because a single action in a UI can lead to many other actions. This complexity makes automating tests essential. End-to-end tests can help automate user-interaction testing, saving valuable time.

Once you’ve decided on the test cases, you can write them as code and integrate them with an automated testing tool. For example, you can use continuous integration to automate the E2E testing of software.

With the speed at which software acquires new features, automating software testing is the only viable option. Automation enables you to catch bugs quicker and more consistently because the entire code base is checked against the test cases each time you add new code.

Conclusion

In this article, you learned what end-to-end testing is and what its benefits and challenges are. You learned techniques for implementing E2E tests on your projects, including horizontal testing, vertical testing, and the distinction between manual and automatic E2E testing.

Manual E2E testing is a great place to start, but you will want to automate your tests as soon as possible for your team. Automation not only saves time and prevents complications, but it also frees your team to do what they do best — develop applications. With AI-powered testing tools now capable of self-healing tests and autonomous test maintenance, the traditional barriers to comprehensive E2E testing are falling.

To implement automated E2E tests, use a CI/CD platform like CircleCI. You can get started in minutes by signing up for a free account today.

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