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

Before you release your product into the market, it is extremely important to properly test whether it’s functioning as intended. To do that, software developers utilize a variety of testing techniques that verify the software’s integrity. To thoroughly check their software from start to finish, developers implement End-to-End testing, often simply called E2E testing – an elaborate technique that mimics end user experience.

There are many layers to End to End testing, as it is one of the most complex testing methods. This type of testing involves testing every part of your software that the end-user interacts with in any imaginable way.

With this guide, we want to show you the importance of E2E tests, as well as tell you precisely what they are, including a few specific examples.

Also see: if you're new to software automation, take a look at this beginner's guide to automation with step-by-step screenshots.

What exactly is End-to-End testing?

End-to-End testing is one of the most useful and informative techniques for software testing, providing valuable data about the inner workings of the program from the end-user perspective. With E2E testing, developers can thoroughly verify the behaviour of their software. During the test, you will be trying to replicate key user behaviour scenarios when using your software. The actual list of things to do varies, depending on the type of software you’re testing – but in all cases, it is rather extensive.

When performing a software testing method, like an End-to-End test on a web application, you would start with opening your browser and navigating to the proper URL, and then proceeding to use the software as intended for the end-user.

Similarly, in the case of a regular desktop application or mobile application, you would open the app just like a user would, checking out every bit of functionality that is intended for the users to work with. Keep in mind that during E2E testing you won’t need to check developer-specific aspects of the software, only the end-user perspective if it is important to you.

End-to-End test goals

During an E2E test, your goal is to verify all of the dependencies and data integrity that directly or indirectly influence the reception of the software by the end-user. This usually includes any external services, as well as databases used by the software and metrics, as well as any other system dependencies.

E2E tests will ideally be performed in the production environment, but this isn’t always possible. The tests can, of course, be performed in an independent End-to-End testing environment, but you should make sure it is as close to the production environment as possible.

Within the SDLC process, E2E tests are performed in the Testing phase, which is situated after Coding and before Deployment.

Why is End-to-End testing important?

Is End-to-End testing necessary? It is true that more and more developers make sure to implement an E2E testing phase before the final deployment of their software. There are many benefits to E2E tests, but the most crucial ones are:

• The ability to verify software performance from the end-user perspective
• Testing verifies not only the software itself but also any interrelated sub systems, increasing test coverage
• Validation of back-end systems
• Immediate end-user-like feedback on test failing

While tests such as unit testing or integration testing are very useful (functional testing), allowing you to verify the working of each component and providing quick results, they don’t give you the whole picture. By not performing E2E tests, you won’t know how the experience of using your software will look like from the end-user perspective.

For example, individual component testing (integration tests) might show promising results and full functionality. However, when combined, something goes wrong and produces a bug. By only checking individual components, you wouldn’t be able to find out about the bug.

With a proper End-to-End test, you can verify whether everything works correctly together as it should. Even integration testing doesn’t cover all of the system components of your software, and you might never know whether every aspect of your app clicks together.

E2E testing doesn’t necessarily have to discover bugs – it can also give you useful insight into the user scenario of your product. Overall, all types of tests play their respective roles in the whole vertical end-to-end testing process (differently to horizontal end-to-end tests). Just because E2E tests give you a more complex understanding of your software as a whole doesn’t mean that other test types are less valuable.

Before releasing your app, always make sure to proceed with a thought-through testing strategy. However, while they’re certainly extremely useful, keep in mind that E2E tests occupy the top of the testing pyramid, making them the most expensive and most difficult to perform.

End-to-End testing is also one of the few functional types of tests that can be performed manually, as well as automated - which is done especially often in Continuous Integration. In such a scenario, a chosen set of tests can be run automatically each time a new iteration is uploaded to the testing server.

Benefits of end-to-end testing

One of the goals of this software testing technique is to simulate the end-user's perspective. This means that this type of testing helps to verify not only the security or performance, but the business aspect as well. It will check whether the software collects and processes data as it was designed to do. End-to-end testing is essential for a comprehensive validation of your product. This testing ensures that all integrated parts of the application work together as expected.

Another purpose of E2E testing is to mitigate risks. E2E testing verifies if the software is ready for deployment. The confidence in stability is a crucial factor which the stakeholders consider while approving the next release.

There are obviously much more obvious benefits of this form of testing (like bug fixing or testing across different user scenarios), but we described them already in this article.

End-to-End Testing Framework

Alright, so now you know what End-to-End testing is – but how to exactly implement it? There is a wide variety of checks and individual tests that must be covered by your end-to-end testing plan, some of which include:

• Establishing test requirements in the preparation phase (including software and hardware requirements)
• Creating proper documentation
• Deciding what type of test environment will be used (production environment or independent test environment)
• Preparation of test cases and general E2E design
• Tracking of data input and output
• Test execution and evaluation

When executing E2E testing methods, developers usually follow an established E2E testing framework that guides you throughout the process, enumerating various tasks and responsibilities. The framework is relatively simple and consists of only three elements:

Establish user functions

The User Functions relates to listing the features of your software, as well as all of its interconnected software systems. To properly measure and test software functionality, you need to first think about what you’re going to test. After you’re finished with listing user functions, remember to record everything relevant to each of them, including both the input and output data. Since E2E testing can be considered holistic, you also need to pay attention to all of the relations between every individual function – how they work together and whether there are any clashes.

Come up with specific conditions

Now that you have established the user functions you’re going to test, you need to think about the testing conditions. Try to come up with as many quantifiable indicators that can be measured for each of the functions. These can range from response time to consistency of data flow, to simple convenience of use. Remember – you’re trying to imagine yourself as an end-user, so try to keep track of anything that might be an issue for a non-developer.

Create individual test cases

Finally, before the E2E testing can commence, you need to prepare specific test cases for each of the conditions. At this point, you have prepared a list of user functions to test, as well as data conditions that will be measured during the test. Now, you need to create at least one test case for each of the conditions. By test cases, we mean user scenarios during which specific indicators will be able to be measured.

And by test case preparation status, we mean the precise location of the test instances being developed, as compared to intended test cases.

End-to-end test cases for your testing process

Congratulations, you’ve almost reached the end! At this point, you should pretty much be a walking fountain of knowledge about End-to-End tests. However, the raw theory is one thing, and implementing those types of tests for system testing in reality is another. To make the process a bit more digestible, consider this End-to-End testing example for a website with shopping functionality:

• Go to the specified URL
• Open a list of products
• Check whether the information on the list correlates with specific product pages
• Try to add the product to the cart and look for visible confirmation
• Navigate to the cart and check whether the product has been successfully added
• Double-check all of the relevant information (price, product info, etc.)
• Proceed with the check-out and verify payment options integration

See how simple it is in the end? Now you can implement E2E testing methodology in your software to ensure better end-user reception, increase your product quality, and build a positive brand image.

This is just a high level example. If you would like to learn how to create a proper test case from start to end, please check out our article on test case creation. You will have a better understanding on how to design test cases for manual and automatic testing. Also check out our other topics in our testing guide.

End to End testing tools

Proper tools may play a crucial role in reducing your effort by automating your end-to-end tests. These tools provide a range of features and capabilities to support horizontal testing and vertical testing of the entire system. They allow testers to perform comprehensive testing processes. Choosing a proper tool for testing is typically a long-term investment. If you research and choose a tool that will enable you to execute and record complex user scenarios and allow testing across multiple technologies, your job will be way easier.

One of the tools that meet such requirements is BugBug. This automated testing tool proved its efficiency for many clients. On the picture below you might see how many steps might an end-to-end scenario actually have.

Summary

End-to-end testing is a type of testing that focuses on validating the whole system from start to finish rather then testing individual functionalities. It is often seen as a software testing methodology, but it is not the case. It may be a part of a methodology (i.e. Agile testing) but it is by definition a type of software testing.

Performing end-to-end testing covers an important task of checking data flows and focuses on testing if any functional gaps occur. This type of testing is necessary to verify if the software is ready for the next release cycle.

Frequently Asked Questions

1. What is automated testing?
   Automated testing in software development is a form of software testing that uses the execution of predefined sets of operations to probe and validate the software system. The fundamental purpose of automation testing in software development is to generate objective feedback about the quality of the product. One such testing tool is Selenium. It can run UI tests. The ideal situation is to run E2E tests with both manual testing and automated testing approaches. If your application has a lot of complicated user interfaces, you'll need more end-to-end testing.

2. What is software development lifecycle?
   Software development lifecycle (SDLC) is the process used by developers to create, deploy and maintain software. This process includes several steps that are all closely connected with one another. These steps include requirements gathering, analysis and design, coding and testing.

3. What is a testing pyramid?
   In software development projects, we have limited time and resources. This is why it's important to consider our test efforts carefully and find the right balance between different types of testing. Basically, there are 3 layers in the testing pyramid: Unit Tests, Integration Tests, and E2E Tests.

4. What is a selector?
   A selector is a small piece of code that describes a specific button in your app. It allows you to clearly define what should be clicked in automated end-to-end tests. You can learn more about selectors using this interactive XPath learning tool

Happy (automated) testing!