End-to-End (E2E) Testing: Stages, Approaches & Challenges

Ensuring that every feature, interaction, and system integration works perfectly is crucial to delivering a flawless user experience. From the user interface to backend systems, it's essential to verify that everything functions as expected. But how can we ensure that every feature works as intended? This is where end-to-end (E2E) testing steps in as a critical methodology. 

What is end-to-end testing?

End-to-end testing is software testing methodology that evaluates an entire application as a user would, from start to finish. The main goal of end-to-end testing is to get a better idea of how the product would behave when used in a live environment. It is a comprehensive way of testing software and identifying where and why problems may arise.

Sitting at the top of the testing pyramid, E2E tests provide extensive test coverage by simulating real user scenarios, which helps in catching critical issues that might be missed during unit and integration testing.

Importance and benefits

A comprehensive end-to-end testing approach is important for identifying potential issues early in the development cycle, reducing the risk of failures in production. This can save time and resources in the long run, as solving issues early on is easier and less costly. It helps with regressions or new issues being introduced when changes are made by executing high-level test cases, which is especially crucial when software is updated and redesigned frequently.

When talking about who can benefit from end-to-end testing, we can highlight two key groups: 

Project managers 

A thorough E2E testing process increases confidence in the product’s readiness for launch, assuring project managers that the system will function as expected. This improves communication with stakeholders, offering clear insights into system performance and helping align team efforts for informed decision-making.

Software testers

End-to-end testing mimics real-user behavior, which allows software testers to prevent potential issues by testing ahead of time. Running E2E tests also helps companies ensure that their software is truly production ready, helping them avoid any major risks post-release. Namely, testing every layer of the application, from APIs to the UI, gives companies full confidence in their system. 

End-to-end testing life cycle stages

The end-to-end testing life cycle involves several key stages, each ensuring that the entire system functions as expected from start to finish. Here’s a breakdown of the main stages:

Test planning

The first stage of end-to-end testing is test planning. This involves providing a clear and precise outline of the testing process timelines, testing approach, and objectives. When planning, you need to define the scope of end-to-end testing, taking into consideration any risks or dependencies that may impact your testing process. Properly defining the test scope will help you focus on testing the most crucial aspects of your system while avoiding unnecessary scenarios.

Designing and developing test cases

The next stage involves creating well-structured test cases that will verify that the implemented features align with the documented requirements. Keep in mind that as the application evolves, so should the tests. Test cases should be reviewed and updated often to reflect the changes in the user interface and application functionality.

You might be interested in: Practical Guide to Creating and Managing Effective Test Cases

Test analysis and execution

The test analysis and execution stage is the most important part in the E2E life cycle, where the actual testing takes place. The testing approach varies across projects, depending on the project’s requirements and complexity, but it can be executed manually or using automation tools. 

Manual vs. automated testing

• Manual testing involves testers manually executing test cases without using any automation tools. The main goal is to uncover bugs, defects, and issues in software applications, products, and systems. 
• Automated testing utilizes automation tools, like Selenium and Cypress, to run tests repeatedly at any time, enhancing efficiency, effectiveness, and test coverage. Automated tests are especially valuable for regression testing and frequent releases.

You might be interested in: Manual Testing vs. Test Automation: A Practical Guide on When to Choose Each

Strategic test execution planning

Planning the timing and execution of test cases is essential to maximize effectiveness. This includes deciding when to run tests:

• Before or after deployments. Running tests before deployment helps catch issues early, while post-deployment testing ensures that the system functions correctly in the live environment.
• Scheduled testing. Scheduling test runs regularly (e.g., nightly or weekly) helps catch issues on a consistent basis.
• On-demand testing. Executing tests as needed is especially useful when new features are added or critical issues need verification.

Monitoring and reporting

The most effective way to provide real-time insights is to use dashboards and reports to monitor test execution. This way, you can easily access:

• Test case status: Pass/fail/in progress.
• Bug tracking: Associating failed tests with specific bugs.

By effectively planning and monitoring test execution, teams can quickly address bugs and ensure that the software meets quality standards before release.

Continuous improvement

The final stage is continuous improvement. Integrate E2E tests into the CI/CD pipeline to automatically run them against new builds. This helps catch issues early and streamlines the development process.

Just like in every aspect of life, continuous improvement is essential. Regularly analyzing test results and adapting your E2E testing strategy ensures that it evolves to better address user needs and emerging challenges. By continuously improving your methods, you can effectively conduct end-to-end testing and ensure your software provides a smooth and user-friendly experience. 

End-to-end testing approaches

To make end-to-end testing as effective as possible, you can lean on different testing approaches. Below, we discuss the two most popular methods for end-to-end testing.

Horizontal testing 

This is the most commonly used approach in end-to-end testing. Horizontal testing focuses on testing complete workflows by evaluating the application from start to finish to check if the workflow functions properly from the user's perspective. It ensures that users can navigate to different parts in the application and perform actions as expected, helping to detect bugs that might have been missed during unit testing. Horizontal testing can be performed at every stage of the business workflow. This method can help you map the requirements to the application developed. Usually, horizontal testing is performed when the environment is stable, at the end of the release cycle. 

Example

Horizontal testing would involve steps like searching for a service, selecting an option, entering user details, proceeding through payment, and receiving a confirmation—all through the user interface to ensure a smooth user experience.

Vertical testing

Vertical testing is typically used for critical modules that consist of complex systems. This method validates the system in layers, conducting tests in sequential, hierarchical order. Unlike horizontal testing, vertical testing focuses on the internal layers of the application’s architecture that do not typically involve users or interfaces. It is usually done when there’s no UI in the system or when the UI is highly complex.

Example

Vertical testing might involve testing the application's API to ensure that it communicates properly with other system components and handles data as expected.

Common tools used in E2E testing

• Selenium. This framework offers extensive support across various programming languages and browsers. Selenium’s flexibility makes it a powerful tool for handling complex testing scenarios. 
• Cypress. A modern JavaScript framework with a visual test recorder that simplifies script creation for common web testing tasks, Cypress is a great option for software testers who want a balance between ease of use and coding control. 
• Playwright. This newcomer from Microsoft is gaining attention for its speed and reliability. Playwright excels in cross-browser testing and can be a valuable asset for teams working on complex web applications. 

You might be interested in: Cypress or Playwright: Which Testing Framework Should You Choose?

• Nightwatch.js. An integrated framework for performing automated end-to-end testing on web applications and websites across all major browsers. Known for its ease of use and simple syntax, Nightwatch.js is ideal for testers who want to write clean, straightforward test scripts.
• Appium. The go-to open-source framework for mobile application testing, Appium allows you to automate tests across various mobile platforms, including iOS and Android, making it a useful tool for mobile-focused development teams.

Challenges in end-to-end testing and how to overcome them

End-to-end testing is a complex process, so it’s expected that various challenges will arise throughout the different stages. What is most important is to be aware of the challenges and to address them proactively.  

Challenge #1: Building workflows

Applications often have a number of functionalities, combining third-party systems, subsystems, and APIs. This can result in thousands of test cases, making it difficult for testing teams to decide where to start.

Solution: Brainstorm key workflows and prioritize critical scenarios. Focus on the most essential use cases first to ensure coverage of high-impact areas.

Challenge #2: Test environment 

Replicating a test environment that mirrors production is not easy, as several elements need to be set up to accurately reflect the live environment.

Solution: Invest in a reliable testing platform that supports integration with other systems and services, ensuring the environment can mimic real-world conditions as closely as possible.

Challenge #3: Long-term maintenance

End-to-end testing is an ongoing process. Every time a new feature is added, you have to create a new set of test cases. This can make it difficult to maintain the existing test suite over time. 

Solution: Establish a clear structure for the test suite from the start and reorganize it regularly. This will help maintain scripts and prevent disruption as new tests are added.

Challenge #4: Test flakiness

End-to-end test suites have a reputation for being unstable. One day the test might pass and the next it may fail. Because end-to-end tests validate different parts of the application, it's difficult to isolate the problem. Sometimes testing teams isolate the issues as a whole, which might reduce the value of the automation suite.

Solution: Track test failures and use testing tools to measure their efficiency. Most importantly, do not ignore flaky tests. By monitoring and analyzing test failures, you can get an idea of where the issue stems from and work on fixing it, ensuring the automation suite remains valuable and reliable.

Challenge #5: Slow test execution

As end-to-end tests cover the entire stack and test all functionalities, the run time can be lengthy. In a fast-paced environment that works best with continuous and constant feedback, long test execution times can negatively affect the efficiency of both the development and testing team. 

Solution: Reduce time consumption by using mocks to simulate the behavior of certain components. You can also pre-configure the necessary data before running tests and structure the test suite to run tests concurrently, speeding up execution and reducing wait times.

Key takeaways

End-to-end testing is crucial for ensuring that every component of your application, from the user interface to the backend systems, functions seamlessly. While E2E testing can be challenging—requiring strategic planning, a stable environment, and ongoing maintenance—the benefits are undeniable.

By overcoming common hurdles like building workflows, managing test environments, addressing test flakiness, and speeding up test execution, you can create a more reliable, user-friendly product that’s ready for the real world.

To keep your testing strategy strong and aligned with your development goals, continuous improvement is key. Integrate E2E testing into your CI/CD pipeline, track results, and regularly refine your approach.

Looking to optimize your QA processes and maximize your testing efforts? Contact us to discover how our software testing services can make a difference.