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Bohdan Mushta, Quality Assurance Engineer

Jan 04, 2024 16 min read

End-to-End Testing: Introductory Guide

This article will discuss the importance of E2E testing, its execution challenges, best practices, and step-by-step instructions on how to do E2E testing effectively. 

End-to-End Testing

End-to-end (E2E) testing is a comprehensive validation approach that examines an entire software system, from its initial phase to the final integration with external interfaces. This testing method is crucial for ensuring the seamless functionality of the software, encompassing aspects such as user interactions and system integrations with external interfaces. This article will discuss the importance of E2E testing, its execution challenges, best practices, and step-by-step instructions on how to do E2E testing effectively. 

What is End-to-End Testing

End-to-end testing is a set of tests encompassing complete business logic and verifying software from start to finish, including its integration with external interfaces. We achieve this by simulating real user interaction scenarios with the system.  

End-to-end testing involves scrutinizing the entire software for dependencies, communication, and data integrity with external interfaces.

Alongside software systems, it also checks the batch processing/data processing from other upstream/downstream systems. E2E testing is typically performed just before deploying the product to end customers.  

 Let’s have a look at the example on how to do E2E testing effectively.  

If we are testing the Facebook website, then end to end testing will include many scenarios like: 

Login

  • Authenticate the user to access their account.  
  • Verify the login functionality and session management. 

Change Profile Picture

  • Allows the user to upload or modify their profile picture.  
  • Test the functionality related to updating user profile information, including file uploads.  

Update Status 

  • Enables the user to share a status or post with their network.  
  • Validate the posting mechanism, content display, and interaction with user feeds.  

Sending Friend Request

  • Initiate a connection request to another user.  
  • Verify the friend request functionality, notifications, and updating of user connections.  

Accepting Friend Request

  • Confirm and establish a connection with a user who sent a friend request.  
  • Ensure the correct handling of incoming friend requests and the update of user connections.  

Blocking and Unblocking Friend 

  • Allows users to block or unblock others, affecting interactions between them.  
  • Test the blocking and unblocking mechanisms, assessing how these actions impact user interactions.  

Checking Notifications

  • Viewing alerts or notifications related to friend requests, messages, or other activities.  
  • Confirm the proper generation and display of notifications and their relevance to user activities.  

Logout

  • Ends the current user session and logs the user out of the application.  
  • Validate the logout functionality and ensure the user's data and session are appropriately handled.  

  

So, end to end testing means checking the whole application from start to end, i.e., from its basic login functionality to complex logic (functionality). 

Why E2E Testing is Important 

With all other testing methods in place, why should we even care for end-to-end testing?  

Simply because E2E testing ensures your software is ready for release. Modern software systems are complex and interconnected; if one of the subsystems fails, the entire system may fail. End-to-end testing can mitigate this risk. 

The process is critical to the success of your application because it provides the following advantages: 

  • End-to-end testing ensures your software is functional from the front to the back end and across multiple systems.  
  • It broadens test coverage and generates new test cases that were ignored before.  
  • Application workflows run smoothly, reducing the likelihood of bugs in production. 
  • End-to-end testing helps reduce the time and costs associated with repeated tests. 

Challenges of End-to-End Testing 

E2E testing is used for ensuring software's overall functionality and reliability, it comes with its challenges. Here are some of the common challenges associated with end-to-end testing: 

Time-Consuming  

  • Complexity: E2E testing involves examining the entire application flow, which can be complex in large software systems. Writing comprehensive test cases and executing them can be time-consuming.  
  • Multiple Scenarios: Since users can follow various paths within a software product, testing every possible scenario could be more practical. Teams often must prioritize and focus on the most critical user workflows, which might require significant time and resources. 

Designing Tests  

  • Real-World Simulation: Designing tests that accurately simulate real-world scenarios is challenging. It includes accounting for different browsers, devices, and user interactions. Ensuring that tests are robust across various environments adds to the complexity.  
  • Maintenance: Tests need to be maintained as the software evolves. Changes in the application's functionality may require updates to existing tests, and failure to do so can lead to false positives or negatives.  

Understanding User Goals  

  • User-Centric Approach: Effective end-to-end testing requires a deep understanding of user goals and how they interact with the application. Focusing solely on features without considering the user's perspective might result in tests that don't align with real-world usage.  
  • User Research Costs: Conducting thorough user research to understand user intentions can be expensive and time-consuming. Sometimes, teams may use a limited set of users as "beta testers," potentially missing out on diverse perspectives.  

Integration Challenges  

  • Third-Party Integrations: Many applications rely on third-party services and integrations. Ensuring these integrations work seamlessly during end-to-end testing can be challenging, as it may involve dependencies on external systems.  

Despite these challenges, end-to-end testing remains crucial for identifying issues from interacting with different components in a real-world setting. Balancing the benefits and challenges, teams often adopt a mix of testing strategies, including unit testing, integration testing, and end-to-end testing, to ensure comprehensive test coverage while optimizing resource usage. 

How to Choose E2E Tests 

When choosing E2E tests, aligning them with the user stories they cover is crucial. Choosing tests that reflect real user scenarios is paramount for practical testing. Regular updates to code and bug fixes can impact product functionality. Therefore, it's vital to periodically refresh E2E tests helping to ensure they accurately reflect the current state of the product.  

We can perform E2E tests manually and with the help of automation testing.    

Manual Testing  

During manual testing, a tester assumes a user's role and uses various devices and screen sizes to assess the application's compliance with the requirements. For instance, while testing an e-commerce store, the tester would follow a user's purchasing process, such as clicking the add-to-cart button, opening the cart, proceeding to the purchase dialogue, and making the payment. The tester aims to identify whether any step breaks or fails to function correctly. 

Types of Manual E2E Testing 

  • Exploratory Testing: Employ for new projects or situations without a clear list of test cases. Testers explore the product, utilizing their intuitive understanding to create test scenarios.  
  • User Acceptance Testing (UAT): Apply to verify whether the product aligns with user requirements, especially before the initial release or in cases involving new testers.  

Automated Testing  

Automated end-to-end testing has the same goal as manual testing - helping to ensure that software performs as expected. However, automated testing offers several advantages that are not possible with manual testing. There are various test automation tools available that provide automated testing services. These tools also offer device labs for testing, which can help ensure that software works across different devices and platforms. 

Key Considerations:  

  • Frameworks: Consider using popular frameworks like WebdriverIO, Cypress, and Appium. They enable the automation of E2E tests and facilitate maintenance.  
  • Regression Testing: Utilize automated tests to verify that new changes do not disrupt existing functionality.  
  • Smoke Testing: Conduct quick checks to ensure core functions are operational after implementing changes or releases.  
  • Cross-platform tools: If your product operates on different platforms, contemplate using tools for testing on various browsers and devices.  

The selected tests should be presented according to importance and coverage criteria, ensuring an efficient check of core functions and detecting potential issues.  

Manual Testing vs. Automated Testing

Manual testing is a process in which a tester conducts tests manually. On the other hand, automated testing involves tests that run automatically. In terms of accuracy, automated tests can be better in many scenarios. 

Manual testing is easier to understand and set up than automated testing, which is often more complex. The learning curve for automated testing is typically higher. 

Manual testing initially requires less financial and resource investment, while automated testing may involve more initial investment. However, as your testing process scales and matures, automated testing offers significant ROI, making it a worthwhile investment. 

In manual testing, it's easier to simulate a product environment. For example, automated tests may encounter a new bug faster than manual testing but configuring them can be complex.  

When to Perform E2E Testing

End-to-end (E2E) testing is performed before the release and after regression testing.   

Performing E2E tests is advisable just before the release and throughout the entire application lifecycle.  

In specific cases, it can be considered for smoke testing and sanity testing, applied after the release is deployed to production, ensuring that everything on production is as intended with no issues. It should be implemented from the initial release and throughout the entire product lifecycle (regression and smoke testing). It is utilized at a different time than the very beginning of the project.  

Best Practices for E2E Testing  

To optimize the effectiveness of E2E testing, a set of best practices has emerged, encompassing strategies to enhance efficiency and maintain a thorough understanding of the product. From deep product knowledge to strategic automation testing investment, each practice contributes to a comprehensive approach that aligns with industry standards and helps to deliver high-quality software.  

Deep Product Knowledge  

Testers must thoroughly understand the product, including business workflows and functional chains, to align testing strategies with end-user expectations. Conduct regular training sessions and knowledge-sharing forums to keep testers well-versed with evolving features and business requirements, fostering a deep product understanding.  

Minimizing Manual Testing and Maximizing Automation

Automated tests are only a universal solution for some software testing scenarios. They have their limitations and cannot address all possible issues.  

While automated tests serve as a universal solution for some software testing scenarios, their capabilities are limited. Initiate an automation setup, gradually decreasing reliance on manual testing. Allocate resources to develop automated test suites, ensuring extensive coverage of critical scenarios and minimizing budget constraints. But keep in mind that automated tests come with limitations and can't address all possible issues.

Strategic Automation Investment  

Strategic automation investment accelerates testing processes and minimizes long-term costs. Prioritize test cases for automation to achieve maximum coverage with minimal effort. Regularly assess the ROI of automated tests, refining the suite in alignment with project goals.  

Test Coverage  

Develop a test strategy identifying essential user flows and critical functionalities. As development progresses, new test scenarios are continually added, specifically tailored for new functionalities.

Regular Test Maintenance  

Keep automated tests up to date to reflect changes in the application and prevent false positives or negatives. Establish a routine for reviewing and updating test scripts in response to changes in the application code. Leverage version control systems to manage and track changes in the test suite.  

Parallel Execution for Efficiency  

Parallel test execution improves efficiency by reducing overall test execution time.  

Use parallel testing capabilities of automation frameworks to run multiple tests concurrently. Leverage cloud-based testing solutions to scale resources for parallel execution, optimizing testing efficiency.  

Continuous Integration (CI)  

Integrating E2E tests into CI pipelines ensures frequent and automated testing with each code change. Configure CI/CD pipelines to trigger E2E tests on code commits automatically. Use CI tools to provide quick feedback on the application's health, enhancing collaboration and efficiency.  

Collaboration with Development Team 

Encourage regular communication through tools like Slack or Microsoft Teams. Establish joint sprint planning sessions involving testing and development teams to align goals, improving overall collaboration.  

By adhering to these best practices, E2E testing can be strategically optimized, providing reliable validation of critical functionalities while effectively managing resources and minimizing manual testing to stay within budget constraints.  

E2E Testing Metrics and Insights  

Among the numerous metrics used for E2E testing are:  

  • Status of Test Case Planning: Determines the specific position of test cases in preparation compared to planned test cases.  
  • Monitoring Test Progress: Test progress should be tracked frequently to obtain information about the test completion percentage.  
  • Status and Details of Defects: It provides a weekly overview of the open and closed defects. Defect distributions are also based on priority and severity on a weekly basis.
  • Environment Availability: The number of operational and testing hours scheduled daily.

End-to-end testing is a highly informative and helpful technique used for software testing. It provides valuable data about the program's inner workings from the end-user perspective. This type of testing enables developers to verify the behavior of their software thoroughly. During the test, critical user behavior scenarios are replicated to identify any potential issues with the program. The exact tasks performed during this test will vary depending on the type of software being tested, but the process is always extensive. 

More and more developers are implementing an E2E testing phase before deploying their software. While individual component or integration testing may show promising results and complete functionality, something may need to be fixed and produce a bug when combined. It is impossible to identify such bugs by only checking individual components. With a proper end-to-end test, you can ensure that everything works smoothly together as it should. 

End-to-End Testing Metrics

Pros and Cons of E2E Testing

End-to-end testing validates the entire system from start to finish, simulating real-world user scenarios. Like any other testing approach, it has its advantages and disadvantages.  

Advantages of End-to-End Tests

  1. End-to-end tests verify the system's functionality across all integrated components, ensuring the software performs as expected in a real-world environment.  
  2. The test means mimicking user interactions, assessing the system's performance in actual usage scenarios, and identifying potential issues or bottlenecks.  
  3. Tests can catch integration issues and dependencies between different system components at an early stage, allowing for timely bug fixes and preventing critical issues from reaching production.  
  4. Successful end-to-end tests assure stakeholders, including developers, testers, and business users, that the system functions correctly, reducing the risk of defects.  

Disadvantages of End-to-End Tests

  1. The end-to-end test can be time-consuming to design, implement, and execute, especially for complex systems with multiple integrations, leading to longer test cycles and increased testing efforts.  
  2. As the system evolves, end-to-end tests may require frequent updates to keep up with changes in the application or underlying technologies, which can add to the maintenance overhead.  
  3. Due to the complexity and time required, covering all possible scenarios and edge cases in end-to-end tests may not be feasible, potentially leaving some areas untested.  
  4. When issues arise in end-to-end tests, identifying the root cause can be challenging as it involves multiple components and interactions, requiring thorough investigation and debugging skills.  

End-to-End Testing Lifecycle  

An effective software testing process consists of four stages: Test planning, Test design, Test execution, and Results analysis. 

  • Test Planning: Planning can be executed at various stages of development. The earlier one initiates foundational planning, the more advantageous it proves. In a test plan, test objectives are defined based on the client's initial requirements and the application's architecture. 
  • Test Design: A suitable test environment is established to ensure thorough testing based on the requirements. Typically, this environment is configured based on previous test runs, allowing testers to use existing configurations. Risk and usage analyses are conducted to allocate resources effectively, ensuring that the test objectives are achieved. Once the test environment is set up, testers create the necessary test cases, utilizing automation testing tools to minimize the time spent on test design.  
  • Test Execution: Test cases are executed both locally and remotely. It is essential to monitor the test progress helping to ensure consistency with the test plan.  
  • Results Analysis: The test results are analyzed carefully to pinpoint the root cause of any bugs. Any such discoveries are then sent to the development team for immediate intervention. After this, a project retrospective meeting is conducted to evaluate the processes and discuss improvement areas.  

How to Do E2End Testing: Step-by-Step Guide  

To perform end-to-end testing, you need to follow a step-by-step approach. The first step is to identify the critical test scenarios that need to be performed. It can be achieved by collaborating with testers, developers, and other stakeholders to identify the necessary testing for use cases before release. 

Once you have identified the test scenarios, the next step is to map out the different steps and actions associated with each scenario, along with their expected outcomes. It will help you create test cases that can be run manually or automated using the right test automation platform. 

While it may not be possible to automate all the tests, automating most tests will help you extract maximum performance and efficiency. Once the tests are automated, you can integrate them into your CI pipeline. It will provide meaningful feedback to the development team and help standardize creating and running end-to-end tests. 

Examples for end-to-end testing.

Scenario: End-to-End Testing Scenario for eCommerce Website: Purchasing Process 

Objective: Validate the entire purchasing process, ensuring a seamless interaction between different components of the website. 

Test Steps:

  • Log in to the website using valid credentials. 
  • Enter the page with the list of products. 
  • Select the desired product from the list that you want to buy. 
  • Add it to the cart by clicking the “Buy” button. 
  • Data Validation in Customer Information Form: fill out the customer information form with valid data and submit. 
  • Payment Information Validation: enter some valid payment information. 
  • Payment Processing: go to the payment processing and complete the payment. 
  • Confirmation Message: close the popped-up confirmation message. 
  • Enter the customer’s order history page. 
  • Verify that the recently made purchase is accurately listed in the order history. 

Postconditions

  • The purchased product is successfully added to the cart. 
  • Confirmation message was displayed after completing the payment 
  • The website's order history displays the recent purchase. 

This end-to-end testing scenario ensures the entire purchasing process is validated, covering interactions from product selection to the confirmation of the purchase in the customer's account. The focus is on seamless integration between different components of the eCommerce website. 

Scenario: End-to-End Testing for User Registration on Social Networking Platform 

Objective: Validate the end-to-end functionality of the user registration process, ensuring seamless user onboarding and account creation. 

Test Steps:  

  • Open the social networking platform's homepage. 
  • Navigate to Registration Page using “Sign up” button. 
  • Complete User Registration Form: fill out the user registration form with valid information (name, email, password, etc.) and press “Register”. 
  • Email Verification: check the registered email inbox for the verification email. 
  • Open the verification email and click on the provided link. 
  • Go to login page using “Log in” button from the platform's homepage. 
  • Login with Registered Credentials: use the registered email and password to log in. 
  • Navigate to the profile setup section. 
  • Verify all values on profile setup section are the same as mentioned while creating an account. 

Postconditions

  • The user account is successfully registered and verified. 
  • The user can log in with registered credentials. 
  • Profile setup is complete with additional details. 

Conclusion 

End-to-end (E2E) testing is a crucial phase in software testing, encompassing the entire business logic and validating software from start to finish, including its integration with external interfaces. The importance of E2E testing lies in its ability to verify software functionality, identify potential issues, and ensure a smooth user experience. It broadens test coverage, reduces the likelihood of bugs in production, and minimizes the time and costs associated with repeated testing. However, E2E testing comes with challenges, such as its time-consuming nature, complexity, and the need for effective test design and maintenance. Balancing its advantages and challenges, E2E testing remains an essential component of comprehensive testing strategies in the software development lifecycle. 

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Frequently Asked Questions

What is the primary purpose of End-to-End (E2E) testing in software development?

E2E testing aims to validate complete business logic and ensure software functionality from start to finish, including integration with external interfaces. 

Why is E2E testing considered necessary despite other testing methods being in place?

E2E testing is crucial as it ensures software readiness for release, addresses risks in complex, interconnected systems, and provides advantages like broadened test coverage and reduced likelihood of production bugs. 

What are the challenges associated with E2E testing?

Challenges include the time-consuming nature, complexity, designing tests that simulate real-world scenarios, maintenance efforts, understanding user goals, and resource intensiveness, especially regarding third-party integrations. 

What are the advantages of E2E testing?

E2E tests verify system functionality across integrated components, mimic real-world user interactions, identify integration issues early, and assure stakeholders of correct system functioning. 

What challenges are associated with E2E testing, and how can they be addressed?

Challenges include the time-consuming nature, complexity, designing tests that simulate real-world scenarios, maintenance efforts, understanding user goals, and resource intensiveness. These challenges can be mitigated by leveraging automation, utilizing cloud-based testing solutions, and adopting strategic testing practices. 

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