What is End-to-End Testing? Definition, Key Components, Types, Automation Frameworks, and More.

While unit testing focuses on a single “unit” of software and integration testing focuses on ensuring that different units work together, end-to-end testing ensures that the entire application works together as expected in a real-world scenario.

NOTE: E2E testing is a part of functional testing and is generally conducted after unit, integration, and system testing processes. It’s usually performed before the software is released to ensure that any bugs or issues are caught before the software is actually used.

End-to-end testing is a type of software testing where the entire application is tested in a real-world scenario such as communicating with the database, network, hardware, and other applications. This testing is done from start to finish under the context of the user’s experience.

End-to-end testing is performed in an environment that closely mirrors production to ensure that the application works as expected when it’s actually used by end users. It’s done from the user’s perspective to ensure that the system behaves as expected when it’s used in a way that a user would typically use it.

Today’s systems are built by combining many smaller parts and technologies. Just because these parts work well on their own doesn’t mean they’ll work well together.

End-to-end (E2E) testing checks that the whole system works as it should, inclusive of all components, integrations, and dependencies. If any problems come up during these tests, go right ahead and fix them to make sure the software works perfectly.

E2E tests look at everything, from the user interface and user paths to the databases and servers, and even other systems and apps that ours needs to work with. They check that everything works, performs well, and is reliable.

Here are some key components to consider while running E2E tests:

Test Environment Setup

The test environment for E2E testing is very similar to the alpha testing environment. Since E2E tests are performed just before the beta release of the software, it's crucial to use a dedicated production-like environment to test your software for proper validation. Here are some things to consider for test environment setup:

• Include relevant hardware, software, network conditions, etc. to simulate real-world conditions.
• Populate databases with real-world test data.
• Ensure that the APIs, databases, external apps, and subsystems are rightly set and integrated like real-world scenarios and that the software dependencies have no issues.

Also Read: STLC: Getting Started with Software Testing

Test Scenarios and Use Cases

Test scenarios outline user interactions with your software. They enable you to represent specific user journeys and align with intended business goals. Here are some key considerations when you outline test scenarios:

• Include important user journeys to test workflows based on your software. For instance, suppose you have e-commerce software. User registration, logging in, searching for a product, buying a product from the wish-list, making a purchase, and so on are some key user journeys to be considered.
• Derive test scenarios from user journeys to target important workflows. For instance, consider two scenarios for e-commerce software: user registration and user purchasing a product.

Here’s what the steps and outcomes look like:

Scenario 1: User registration

1. Steps: Navigate to the registration page, enter valid details, submit the completed form, and confirm user email.
2. Expected outcome: User account is created successfully.

Scenario 2: User making a purchase

1. Steps: Login to the software, search for a product, add to cart, proceed to checkout, select an address, and make payment.
2. Expected outcome: Payment is successful and the order is placed.

• Consider exhaustive test scenarios including invalid test inputs, variable inputs, and edge cases.
• Ensure that your software is fault-tolerant and has well-managed error-handling mechanisms.
• Include test scenarios for integration points like APIs, databases, authentication, third-party apps, etc.
• Simulate multiple users performing various actions like registering, making purchases, etc. to create and execute effective test scenarios.

Integration Points

Since E2E testing subjects fully integrated software to identify issues and benchmark its capabilities, the interactions among the system components are tested for validation. Here’s what to test in E2E testing while validating integration points:

• Ensure that the interaction points, data and control flow, and various modules of the integrated subsystems are error-free and function together seamlessly.
• Test and validate that API endpoints, requests and responses, authentication workflows, and error handling are as per the specifications.
• Validate that there are no compatibility issues between your software and integrated subsystems.
• Ensure that the database queries respond as expected for data creation, retrieval, update, and delete actions.
• Validate the database workflow functions as per the specified or intended business logic.
• Ensure error-free, secure, and smooth interaction between your software and third-party or external applications like cloud providers, payment gateways, authentication and authorization gateways, etc.
• Ensure there are no performance issues or bottlenecks with the integrated system in case of traffic surges or variable network conditions.

UI Functionality Testing

UI functionality testing helps ensure an error-free run and a consistent UI across your software. Here’s what to test in UI when you perform e2e tests for software:

• Ensure that UI elements like buttons, menus, fields, navigation, forms, etc. work as expected in terms of functionality, usability, and performance.
• Identify and resolve issues that negatively affect user experience. These include elements that are inaccessible, malfunctioning, misplaced, or elements that obstruct important user flows.
• Ensure that the UI works and functions align with project requirements and intended business goals.
• Ensure that there are no data inconsistencies when your frontend fetches them from your backend.
• Ensure that your frontend can handle invalid user inputs or when it throws an error with proper messages or instructions for what happened and what to do next.
• Validate the responsiveness of your software so that it adapts as per user devices.
• Ensure that UI elements display correctly in different languages and locales.

Also Read: Top 24 Chrome Extensions for Testers in 2024

Manual testing is when someone tests the whole system by hand to find problems that automatic tests might miss. It’s important because it uses the tester’s own skills to check how well everything works together. These tests can be written down and later turned into automatic tests.

Let’s briefly cover the two manual end-to-end testing types:    

Horizontal End-to-End Testing

Horizontal end-to-end testing covers the entire system (APIs, subsystems, databases, layers) to identify and resolve issues.

Also Read: Types of Software Testing Tools

For instance, when a user successfully buys a product in an e-commerce application, it involves many layers of functionality coverage and validation like searching, adding to the cart, payment, and transaction gateways, email order confirmation, etc.

Vertical End-to-End Testing

With vertical end-to-end testing, you test and validate each layer of your software, from the ground up, and ensure that every layer functions well on its own. You identify and report bugs from erroneous layers to get them fixed.

This means that you start with the unit tests at the database level and subsequently move to the top layers testing each layer covering the entire system.

For instance, suppose you’re testing for the payment and transaction gateway in an e-commerce software. In vertical testing, you use the payment gateway as a part of all the subsequent layers that interact with it to make up the payment gateway function well.

Automated end-to-end testing is employed for tests that are not feasible with manual methods. Automated frameworks and tools are widely used to conduct automated end-to-end testing. It’s a lifesaver when it comes to long-running, repetitive, and complex tasks.

For instance, a single user action may affect many other results simultaneously. Automated frameworks can handle such complexities brilliantly while conducting end-to-end tests. Complex applications can significantly benefit from it and therefore, end-to-end testing is generally performed using automation frameworks and tools.

Also Read: Hot Automation Testing Tools in 2024

Here are the top end-to-end automation testing frameworks:

Selenium

Selenium is one of the top automation tools for web browsers with solid end-to-end UI testing capabilities. Selenium supports multiple programming languages, browsers, and other frameworks.

Key Features of Selenium

• Multi-platform support—Windows, MacOS, Linux, and UNIX.
• Multi-language support—Java, Python, C#, Ruby, JavaScript, Kotlin.
• Cross-browser testing support—Chrome, Safari, Firefox, etc.
• Offers a suite of tools—Selenium WebDriver, Selenium IDE, and Selenium  Grid.
• Record and playback feature—to capture and analyze user interactions while testing.
• Parallel testing execution capabilities.
• Support for CI/CD pipelines.

Selenium Pricing: Open-source and free to use.

Pros of Selenium

• Offers flexibility to choose from multiple languages to write and test scripts.
• Wide adoption across the software industry—huge community support and tons of available resources.
• Strong integration capabilities with other tools like Jenkins, JUnit, TestNG, Cucumber, etc.
• Supports multi-tabs while testing.
• Supports mobile testing (using Appium)

Cypress

Cypress is a JavaScript end-to-end testing framework for web applications. Cypress’ popularity is skyrocketing especially among the modern frontend developer community. You can also perform component testing, unit testing, and integration testing with Cypress.

Also Read: Unit Testing vs. Integration Testing

Key Features of Cypress

• Supports real browser testing to mirror real-world usage and user experience.
• Time travel feature for real-time visual debugging that lets you hover over each executed command to diagnose any failures and monitor testing steps.
• Auto-wait feature for elements to be actionable before performing actions to handle async code execution.
• Configurable network traffic conditions.
• Supports BDD and TDD testing strategies.
• Flaky test management feature on Cypress cloud to avoid flaky test results.
• In-built test management dashboard, analytics, and reporting on Cypress cloud.
• Smoothly integrates with CI/CD pipelines and project tools.
• Offers advanced features on Cypress cloud like parallelization, load balancing, etc. for better test orchestration.

Cypress Pricing: Available for free with three paid tiers.

Pros of Cypress

• Supports cross-browser testing for Chrome and Edge family browsers
• Easy-to-use APIs with clear and comprehensive docs for enhanced developer and user experience.
• Easy setup.
• Faster test execution due to efficient async code handling capabilities.
• Separate driver installation is not required.

Playwright

Playwright is an open-source Node.js-based end-to-end testing framework for modern web applications.

Key Features of Playwright

• Cross-browser support for Chrome, Safari, Firefox, Edge, and Opera— ensuring tests are compatible with all modern rendering engines.
• Cross-platform capabilities—allows testing on Windows, Linux, and macOS.
• Supports multiple programming languages—JavaScript/TypeScript, Python, .NET, and Java.
• Auto-wait feature to pause test/code execution to avoid flaky tests.
• Tracing and test retry strategy with execution trace, videos, and screenshots to debug tests.
• Browser contexts for full test isolation and fast execution, with the ability to save and reuse authentication states.
• Powerful tooling with code generation, Playwright inspector, and Trace Viewer for test creation and debugging.

Pricing: Open-source and free to use.

Pros of Playwright

• Supports cross-browser testing for all modern browsers.
• Provides a high-level API for fast and stable interaction with the web browser.
• Allows testing of mobile web applications with native mobile emulation.
• No limitations on testing scenarios, supporting multiple tabs, origins, and user interactions.
• Offers powerful debugging tools and a rich set of introspection events for reliable test execution.

Let’s cover end-to-end testing vs. integration testing to get a lowdown on the key differences between them:

End-to-end testing not only helps to test your entire software but also ensures that its complexities do not hinder user experience or user interactions in any way.

By scrutinizing the entirety of your software, from the test environment to UI functionalities, end-to-end testing provides rock-solid ways to ensure polished software to champion real-world conditions.