What is End-to-end (E2E) Testing?

End-to-end testing is a methodology used in the software development lifecycle (SDLC) that tests the functionality of an application from start to finish under real life circumstances.

The goal of end-to-end testing is to simulate what a real user scenario looks like. The completion of this testing is not only to validate the system under test, but to also ensure its sub-systems work as expected.

Why Is End-to-end Testing Important?

Software is becoming more complex every day. Applications are built on layers and entire networks of sub-systems. This includes UI and API layers, external databases, and networks. And when one fails, so does the entire product. This makes the stability of each component vital to the success of the application.

This means you need to test the entire application, including both the API and UI layers, from start to finish. For the best results, you should create and execute tests using test automation tools. This allows you to maximize coverage and ensure quality on all application layers.

Types of End-to-end Testing

The two types of end-to-end tests are horizontal and vertical. Let’s look at both:

Horizontal E2E Testing: This checks a specific layer or component works consistently across different parts of your software.

For instance, if you have a messaging app, horizontal testing will ensure that sending messages works well on different devices, like phones, tablets, and laptops.

Vertical E2E Testing: This ensures a particular function works smoothly from the front-end interface down to the server and database.

If we stick with the messaging app example, vertical testing will verify that not only can you send messages across devices, but the whole process works — from typing a message, to the server processing it, to the recipient getting it.

Benefits of End-To-end Testing

Conducting end-to-end testing will ensure your software is production-ready so you can deploy with confidence. The process is essential to your application’s success for a few key reasons:

  • Confirms Application Health: Validates your software is functional at every level — from the front end to the back end and on multiple systems.
  • Expands Test Coverage: By incorporating different sub systems in your testing process, you’ll expand test coverage and create additional test cases.
  • Detects More Bugs: Find and fix issues faster. This will reduce the chances of bugs making it further into the testing process or into production.
  • Reduces Testing Effort & Cost: Fewer bugs means you can repeat tests less, and reduce the costs associated with doing so.

Challenges of End-to-end Testing

While end-to-end testing offers comprehensive insights into an application's functionality, it comes with its own set of challenges:

  • Complexity: As applications grow in complexity, E2E testing demands meticulous planning and can become time-consuming.
  • Resource Intensiveness: As tests become larger and more complex, it requires more time, personnel, and testing environments.
  • Maintenance: Applications frequently undergo updates, which leads to continuous adjustments in tests to reflect these changes.
  • Environment Variability: Differences in test environments and data can impact test results. Maintaining environments across different stages of testing can be difficult.

Best Practices of End-to-End Testing

To overcome these challenges and maximize the effectiveness of your end-to-end testing, consider the following best practices:

  • Prioritize Test Cases: Not all scenarios need equal attention. Prioritize test cases based on their impact on critical functionalities.
  • Test Automation: Automate repetitive and time-consuming test cases to ensure consistent execution and quick feedback.
  • Continuous Monitoring: Implement continuous monitoring and feedback to catch issues early in the development cycle.
  • Collaboration: Foster collaboration between development, testing, and key stakeholders to ensure a holistic testing approach with quick feedback loops.
  • Tagging: Process of adding metadata to test cases or test suites to describe their content or purpose. This can be done manually or automatically, and the tags can be used to filter and organize tests, run specific tests, or track test results.

End-to-end Testing with SmartBear Tools


SmartBear tools TestComplete and ReadyAPI support automated UI and API testing, respectively. And with the integration between the two tools, you can pass values between them to validate steps at all layers. This means you’ll be able to speed up release cycles, cut costs, and ensure quality for your customers.

Test Reusability

SmartBear tools allow you to reuse your UI and API tests. Share test data between UI and API layers for maximum efficiency.

Reduced Maintenance

As you build out larger regression suites and tests, test maintenance can become a burden to Agile and DevOps teams. Update data and assertions in centralized project systems.

Easier Test Creation

Both tools enable both technical and non-technical testers to create and automate tests. Automate even the most complex scenarios with easy to use and intuitive interfaces.

Dynamic Execution

Execute your API and UI tests in conjunction with your test management tool and CI/CD pipeline. This allows for dynamic execution in nearly any environment.

Variety of Integrations

Integrate with the tools in your existing workflow to complement your DevOps toolchain. Click to see all TestComplete and ReadyAPI integrations.

Try It Out Yourself

End-to-end testing may have its challenges, but it can also empower you to validate every aspect of your application. By simulating real-world scenarios and interactions, you can be confident that you’re delivering the best user experience, every time.

Ready to try end-to-end testing? Start a free trial of TestComplete and ReadyAPI today. Experience all of SmartBear’s tools.