Comprehensive Guide to End-to-End Testing

In this detailed guide, we cover the importance of end-to-end testing for delivering quality software consistently, its fundamental principles, methods, and practical insights to make your E2E testing process efficient and scalable.

What is End to End Testing?

A proper introduction to end-to-end testing or E2E is due. As I mentioned, there are many testing processes and methods for an application during development.

However, most of them only focus on one aspect of the app or software. End-to-end testing is slightly different from your typical functional or non-functional tests.

Scratch all that for a moment. Think of the whole flow of your software from a user's perspective (hence the reasoning behind the name end to end). Let's assume that we're talking about getting a user signed up to your site and getting them an account/identification.

In end-to-end testing, you would assess this whole workflow and ensure that everything runs fine in that test scenario. Moreover, it's not only limited to testing your codebase.

Instead, it also tests all of the external dependencies — be it a library you're dependent on or something else. Given this structure, end-to-end testing is also known as chain testing by many developers and testers.

These tests attempt to imitate real-life scenarios that a user may face. This replication of user experience and behavior makes it highly critical to ensure that the released build fulfills all expectations.

These tests are usually pretty chunky and require more time and resources to run (more on that later). First, let's look at an example of what an E2E test may look like, at least if this is your first rodeo.

How an E2E Test Looks?

The easiest way to explain something as complex as software testing is probably through an example, so let's imagine a use case.

Let's say you have some form of mailing service, and you want the features to be tested. What are the things that you would test?

You would want to get the users signed up or get them to log in first. Then, they should be able to send or check for emails, compose and send new ones, check different parts of the inbox, etc.

The flow could be like: getting to the site, signing up or logging in, checking for new emails, accessing folders like spam, sending replies and new emails, and correctly signing out once they're done.

An E2E test will check all of these things step by step and see whether all integrations are performing ideally. Of course, an actual test would be far more complex and include various intricacies. You'd also have to test the dependencies (for instance, checking whether the integration with the database is working well when you're fetching the user's credentials).

Given how vast this can be, how do you even know what your end-to-end test should look like? Let's get a glimpse of that too.

Why Should You Do End to End Testing?

E2E tests are large and chunky. They can be hellish compared to the baby unit tests or API call tests. And hence, the question of importance is a rather crucial one to ask here.

  • Extended Test Coverage: E2E testing broadens the test coverage for your codebase. In addition to testing the application, it validates all of the third-party codes and dependencies. That's essential to validate the whole flow of the product.

  • Looking at It from a User's view: Typical unit tests do a good job of validating small components, but they cannot emulate the position of an actual user. That drawback can overlook errors that would only be visible during usage. End-to-end tests manage to identify those errors by looking at the software from an end user's perspective.

  • Fewer Errors in the Production Environment: There is a chance of overlooking errors that may only be apparent during real-world usage. Furthermore, not testing everything can leave minor discrepancies undiscovered.
    End-to-end testing reduces that risk and results in a more stable and error-free build in production.

  • Minimizing Cost and Time: For one, E2E testing has a more extensive code coverage, meaning it validates everything you need to validate at once (as opposed to only testing the parts of the code you have made changes to). Since this minimizes the possibility of having to debug the application down the line again, it saves you money and time in the long run.

  • Consistency in User Experience: E2E testing covers everything from the front-end to the back-end for many scenarios and use cases. All of the scenarios go through a similar testing standard, including the integration with other applications. This streamlines the user experience and makes it more consistent.

Challenges of End to End Testing

  • Flaky Tests: Test flakiness is a common issue with E2E, meaning the test may fail after succeeding without making any changes to its code. What makes it worse is that the vast nature of these tests makes it tougher to identify or isolate the root of the issue. Continuously tracking the failures in test cases can help you identify and minimize these.

  • Maintenance: Given how extensive E2E tests are, they tend to be pretty huge. That makes it challenging to maintain the test suite over time. It does help if the testers keep the test suite lean, but it still gets tough to maintain (especially when you're adding or removing test cases).

  • Sluggishness: E2E tests have managed to build a reputation for being slow. That's entirely normal, considering how they validate the whole workflow and test every application component. Nevertheless, a slow test can hurt the efficiency of the test and may create bottlenecks.
    Using tools that can run tests in parallel can help cut the time down. Utilizing stubs and mocks can also be a reliable way to save resources.

  • Integrating Multiple Tools and Systems: End-to-end tests have to connect to a whole host of applications. For instance, a typical E-Commerce platform would have CRM tools, tracking systems, payment gateways, or shipping services. In addition, the tests will be run on multiple platforms and browsers, which is also something you have to account for. This integration between many platforms and tools can be tricky.

Who Does End to End (E2E) Testing?

In this messy who does what world of software design and development, things are done in many ways. But let's try to answer that question holistically.

Typically, QA professionals are the right people to get the E2E testing done. That's not just the case for an end-to-end test — they are the usually right people to get most software tests done. But that doesn't always have to be the case.

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Do Developers Do E2E Testing?

Now, it may not sound feasible for a small team to assemble a whole QA team. We see that even the devs sometimes do end-to-end testing in many cases. Many companies are now getting the developers to do it by default, regardless of their size.

There are opinions for and against this idea. Here are some reasons why people don't like it:

  • The first reason is that these are the same people who wrote the codebase for your software. That introduces the possibilities of a few things — one; they typically won't look at things from an end user's perspective, which is crucial for these tests.
    Secondly, that position may open them up to personal biases (even though they may be unintentional). Therefore, having a neutral perspective on the whole thing can be helpful.

  • Another aspect is that these devs are already bearing a huge responsibility. Adding even more stuff to that burden is probably not the ideal step. It also reduces your team's efficiency in terms of getting the build out there as soon as possible (remember the crunch days?). The reason is straightforward — the devs would be spending a lot of time on QA testing.

However, there are arguments for devs doing these tests as well. That's partly because they know the codebase and every little intricacy within it. Another reason is that running end-to-end tests can give them a more significant incentive to do an even better job of writing better code from the very beginning.
Regardless of the opinions, it's evident that while QA professionals are one of the best people for E2E tests, the options aren't limited.

When Should You Do End to End Testing?

The when of end-to-end testing is quite crucial. These chunky tests take time to design, script, and run. Therefore, knowing when to do end-to-end tests can make the whole process more efficient.

The Testing Pyramid

Typically, you'll find a few tests done multiple times during the development cycle.

A helpful bit, in this case, would be the notion of the testing pyramid. It talks about pragmatically doing things — finishing the smaller and more focused tests first and climbing up the higher complexity and scope ladder.

For example, we should always do a unit test before moving on to integration testing. The rationale is straightforward — unit test verifies the smallest units of code in the software's codebase, and finding issues from a single unit would be very quick.

Following that same rationale, E2E testing should start after tests with lower coverage, but higher efficiency and speed are done. Otherwise, the E2E test would take more time, and resolving issues would take longer due to the broader test coverage.

We may not similarly do things as we did with development models like Waterfall. Nevertheless, we can still utilize that same testing pyramid principle to avoid redundancies and inefficiencies.

End-to-End Testing Life Cycle

End-to-end testing is a comprehensive approach that tests an entire application flow from start to finish to ensure that all components work seamlessly. The end-to-end testing life cycle consists of several stages, which are described below in more detail:

  • Planning: In this stage, the scope, objectives, and resources for end-to-end testing are defined. This includes identifying critical paths and dependencies, as well as determining the testing approach and techniques to be used.

  • Test Design: In this stage, test scenarios and cases are developed based on business processes. Input data and expected outcomes are also specified. This stage is critical, as it ensures that testing is thorough and covers all possible scenarios.

  • Environment Setup: In this stage, the test environment is configured to closely mirror the production environment. This involves setting up databases, servers, networks, and other dependencies. The environment should be set up to ensure that it is stable and reliable.

  • Test Execution: In this stage, end-to-end test scenarios are executed, and the results are monitored and logged. This stage involves validating that the application works as intended and that all components are integrated correctly. Any issues or failures are identified, and their severity and impact are assessed.

  • Defect Logging: In this stage, defects and issues found during test execution are recorded. This stage also involves prioritizing the defects based on their severity and impact. The goal is to ensure that the most critical defects are addressed first.

  • Defect Resolution: In this stage, developers resolve the identified defects. The fixes undergo testing to ensure that they do not introduce new issues. This stage is critical to ensure that the application is stable and performs as expected.

  • Regression Testing: In this stage, previous tests are rerun to ensure that new changes have not affected existing functionalities. Regression testing is critical to ensure that new changes do not break any existing functionality.

  • Reporting: In this stage, comprehensive reports are generated that detail test results, including pass/fail status, defects found, and overall test coverage. This stage helps stakeholders understand the testing process and the quality of the application.

  • Sign-off: In this stage, stakeholders provide approval for the application release based on test results and stability. This stage is critical to ensure that the application is ready for release and meets the desired quality standards.

Types of End-to-End Testing

  • Business Process Testing: This type of testing is used to validate end-to-end workflows, ensuring that all business processes function correctly.

  • Scenario Testing: This testing evaluates real-life scenarios, simulating how users interact with the application to identify any issues or deficiencies in the system.

  • Data Migration Testing: This testing ensures that data is migrated correctly across different components, verifying data integrity and accuracy.

  • Integration Testing: This testing verifies seamless interaction between different modules, systems, or services to ensure that the system is working properly.

  • User Acceptance Testing (UAT): This type of testing validates if the system meets user requirements and expectations, ensuring that it's ready for deployment.

How to Perform E2E Testing?

Scoping, Planning, and Setting up the Test Environment

  • Firstly, we need to list all the essential features and functions that the users of your application would come across. The extensiveness of those functions and flows can differ depending on your application. You require a clear notion of how each function should work and how the relationships between them should be.
    Sure, testers would love to test every little function that the end-users interact with. However, that's not feasible regarding resources and the time taken. That's why it's vital to know what to choose.

  • Many teams utilize user data to figure out what to test as well. But that does assume that you have a large enough userbase and the data required to help you with that.

  • Once the requirements are set, the next step is to get the test environment up and running according to those requirements.

Defining the Conditions and Designing the Test Cases

Now that we have the groundwork laid out, we can build conditions on top of them. Testers should have a clear notion of how each of them should respond. A well-defined test is crucial for a quality application, so all test scenarios should be clearly defined and described.
After that, testers can move on to designing the test cases. They have to add the assumptions, pre-conditions, and required data — the usual deal.

Test Execution and Results

The next step is to run the E2E test. The testing tool will go through all test scenarios to validate every crucial user function and return with insights.
Utilizing those insights is a crucial part as well. Testers need to track the test progress at regular intervals and have clear metrics to determine the application's success.

Strategies for E2E Testing

Horizontal vs. Vertical Testing

  • E2E testing is of these two types. Horizontal E2E testing is the most common one, which tries to validate every bit of an application's flow. It does so by going through every unit or application from the beginning and ensuring that the integration is error-free. This method is helpful considering how many different integrations and dependencies applications have these days. Horizontal testing allows testers to focus more on the end user's experience.

  • Vertical testing takes more of an independent approach to things than horizontal testing's holistic one. It goes through different layers separate from each other and works its way up.
    Vertical tests can be faster since they separate the layers from one another. That can result in higher coverage of the codebase and be more focused.

While both have their advantages, many testers opt for horizontal testing because of how much more control they can have over it.

What is the Difference Between E2E and Regression Testing?

The difference between regression testing and end-to-end testing is that while regression testing ensures that what worked yesterday still works despite any modifications in the SDLC, end-to-end testing involves testing a business process as a whole from start to finish.

Let's have a look at End to End testing vs Regression testing key differences:

End to End TestingRegression Testing
End-to-end testing is used to ensure that the software functions correctly from start to finishRegression testing ensures that software changes have not caused any new bugs.
End-to-end testing can be more time-consuming as it tests the entire software system from start to finishRegression testing is done more frequently than end-to-end testing. Which also consumes less testsigma_other_tools
End-to-end testing, on the other hand, is a much more comprehensive testing methodology that tests all aspects of the system from start to finish.Regression testing is typically done after a code change to make sure that the code change did not break any existing functionality.
Workflow is the main focus in end-to-end testingIt concentrates on making sure that new developments don't break already existing capabilities
Checks the efficiency of business operations by identifying problems with integrations or subsystem Tests replicating the end-user experience in the real world are simulated in the production environment.Verifies the smooth operation of business processes by verifying that system updates do not affect the functionality of legacy code Tests are stimulated in the pre-production environment
Throughout the SDLC, tests are regularly executedTests are conducted only after a programming modification or release
There must be generated or new test casesThere are existing test cases; they will be repeated

The broader range of testing coverage is a significant and shared benefit of end-to-end and regression testing. The most important lesson for businesses considering using any of these testing approaches is that, despite the abundance of benefits, each has a considerable amount of maintenance baggage to deal with.

End-to-End Testing vs Functional Testing

CriteriaEnd to End TestingFunctional Testing
ScopeEncompasses the entire application flow.Focuses on individual functions or components.
ObjectiveValidates system behavior in real-world scenarios.Verifies specific functionalities or features.
ComplexityGenerally more complex due to involvement of multiple components.Less complex as it deals with isolated functionalities.
DependenciesIdentifies and tests interdependent components.Does not consider inter-component dependencies.
CoverageOffers broader coverage of the application.Provides specific coverage based on functional requirements.
Execution TimeTends to have longer execution times due to the comprehensive nature.Typically has shorter execution times for targeted functionalities.

End-to-end testing ensures that all components work harmoniously, mimicking real-world scenarios, while functional testing zeroes in on specific features or functions within the application.

Common Tools and Frameworks for E2E Testing

The automated testing market is growing more and more saturated every day, and we've got tons of options to pick from. Here are a few of them:


Since its inception, Cypress has managed to gain a considerable amount of popularity among testers for its unique design. Unlike most of the other tools here, this one focuses entirely on end-to-end testing. This tool is open-source, and it has been developing pretty quickly.
Writing tests with Cypress is pretty effortless, and it doesn't require any external dependencies either. It supports frameworks like Angular and React flawlessly and supports cross-browser testing. Devs who follow a test-driven development approach like this tool because of its real-time capability.
There's one caveat: it doesn't work on Safari yet. That can be a bummer for a lot of testers.


We've got a testing tool that focuses on BDD (behavior-driven development). This is another open-source tool, and it's written with Ruby. One of the best things about this tool is its simplicity and ease of usage.
It uses a language called Gherkin for test scripting. The fun bit about this language is that it's close to writing tests in English. As a result, even non-technical testers can learn to write the tests with Cucumber pretty quickly.


Selenium is one of the most well-known software testing tools out there. It has been around for a long time, and you can find packages for a plethora of languages, including JavaScript, Python, Java, and many more. This sort of versatility is very handy.
Furthermore, it has a long list of functions, making it easier for you to test all sorts of case scenarios. Selenium's test coverage is pretty impressive for that reason. It also allows for parallel execution, which is beneficial for extensive and frequent tests such as E2E tests.


Unlike Cypress, Testsigma covers a broader range of software tests (obviously including end to end testing). With its scalable automated testing, you can even integrate the testing between different parts of your application.
It allows for both cloud and offline deployment, which improves accessibility. The usage of AI also means that little changes won't break the test. This tool also supports cross-browser testing and parallel execution. It's also a suitable option if you go for data-driven testing.

End to End Testing in Agile

E2E testing has made itself a crucial part of every little sprint when you're developing in agile.
Typically, we focus on a single unit or part of the software during each sprint. While that does mean that we're working on the codebase of a single component or sub-system, it does not mean that it won't affect the rest of the application. Therefore, it's paramount to test whether the rest of the product's workflow is running fine.
That's where end-to-end tests can come in to save the day. It's undoubtedly the efficient way to ensure that the whole system maintains the flow the way you want.

What are the challenges of E2E testing:

Organizations and quality engineering teams often face several challenges in end-to-end testing:

  • Complexity of Systems: In modern applications, multiple interconnected systems, APIs, and databases need to function seamlessly. Ensuring that all these components work together flawlessly becomes a challenge due to their complexity.

  • Data Management: Managing realistic and diverse data sets for end-to-end testing can be cumbersome. Ensuring accurate data at each stage of testing, including edge cases, is vital.

  • Test Environment: Setting up an environment that accurately mimics the production environment can be difficult. Variations in configurations and network conditions may lead to inconsistent results.

  • Dependency on Third Parties: If the application relies on third-party systems or services, it becomes challenging to control their behavior, leading to potential disruptions during testing.

  • Execution Time: End-to-end tests involve multiple steps and interactions, making them time-consuming. Waiting for all scenarios to execute and validate can slow down the testing process.

  • Maintenance: As the application evolves, end-to-end tests may need frequent updates to accommodate changes. Keeping test scripts up to date and relevant becomes a challenge.

  • Identification of Root Causes: When failures occur during end-to-end testing, identifying the exact root cause can be complex due to the interconnected nature of systems.

  • Test Data Consistency: Ensuring consistent test data across different test environments and cycles is challenging. Mismatched data can lead to false positives or negatives.

  • Scalability and Performance: Testing the application's performance and scalability under varying loads and conditions requires careful planning and resources.

  • Feedback Loop Delay: Longer test execution times and complex debugging can delay feedback on code changes, affecting the agile development cycle.

  • Resource Allocation: Allocating resources and infrastructure for end-to-end testing can be resource-intensive, impacting other testing phases.

Overcoming these challenges requires a well-structured testing strategy, automated testing frameworks, and collaboration between development and testing teams.



In this age of complex software design and quick iterations, end-to-end testing is one of the most efficient ways to keep your application running flawlessly. While these tests are comparatively chunkier and require more work to write, they're irreplaceable if you want to ensure a quality experience for the end-user.

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