End to end and integration testing are both critical in creating comprehensive test automation, yet they offer different focuses and scopes. In this article, we’ll guide you through the fundamentals and key differences of these two types of testing.
End-to-end (E2E) testing is a software testing technique that verifies the software functionality in its entirety from start to finish. It involves testing a complete workflow, starting from the user's entry point to the application's final output, and ensuring that the system functions correctly as a unified entity.
In end-to-end testing, testers replicate live data to simulate real-world user scenarios, covering all the steps that a user would take to perform a particular task. For example, in a shopping application, end-to-end testing would involve testing the login functionality, user registration, shopping cart, checkout, and payment processing.
Such user flow can appear to be linear and straightforward on the interface, but under that surface are hundreds of components communicating with one another, from APIs, databases, to networks and third-party integrations. End to end testing aims to verify the application’s flow of information, including all related paths and dependencies.
The main purpose of E2E testing is to validate that all the system components can run under real-world scenarios. This can be broken down into:
In this scenario, a customer searches for available rooms on the hotel booking website. He then selects a room, books it, and verifies that the booking is successful. Below are the possible test cases:
In this example, end to end testing covers the entire booking process on the hotel website, from searching for available rooms to receiving a confirmation email. It also verifies that the website elements (search bar, payment gateway, email notification) meet all functional requirements and work seamlessly with each other.
There are 2 approaches to performing end to end testing.
Horizontal E2E testing is done from the viewpoint of users, where the focus is on simulating specific use cases and navigating through them from beginning to end. This involves every customer-facing aspect of the application such as the user interface or application logic.
For example, in a shopping site, horizontal E2E testing may involve testing the checkout process, from selecting a product to completing the purchase. It would be used to verify that the product is added to the cart, customer information is collected, the payment is processed correctly, and the order is confirmed.
Vertical E2E testing is a more technical approach that focuses on testing in layers or levels following a hierarchal order. Individual layers of the application are tested from top to bottom. Vertical testing is often used to evaluate complex computing systems that do not involve interfaces such as databases or API calls.
Read more: Top 10 Best End-to-End Testing Tools and Frameworks
After the completion of unit testing and prior to end-to-end testing is integration testing, where multiple modules are tested as a single unit. Software typically comprises various modules built by individual developers. Each code unit may have been developed with specific requirements, functionalities, and constraints in mind, and their combination may result in unexpected behaviors or errors.
Integration testing involves testing the interfaces between the modules, verifying that data is passed correctly between the modules, and ensuring that the modules function correctly when integrated with each other.
Read more: Unit Testing vs Integration Testing: What are the key differences?
The objective of integration testing is to put all the modules together in an incremental manner and ensure that they work as expected without disturbing the functionalities of other modules
In the case of a ride-hailing application, below are some possible integration test cases:
Read More: Top Integration Testing Tools You Should Know
Integration testing can be done using many different approaches, with the 2 most common being the big bang and the incremental approach. In the first approach, all the components are integrated all at once, and then the entire system is tested as a whole. The Incremental approach, on the other hand, breaks down the software into manageable and logically related modules and tests each bundle before integrating them into the complete system.
The incremental approach is further divided into 2 methodologies:
A top-down approach involves testing the higher-level components of a software system before testing the lower-level components. Developers often use stubs to simulate interfaces between the unavailable or underdeveloped lower lever modules.
For example, the ride-hailing application above can include these modules:
For an incremental approach, the following test cases can be delivered:
In this method, testing lower-level modules is prioritized, followed by the higher-level modules. This ensures the reliability of the foundational modules before moving to higher-level ones.
In case the top modules are not in a ready state for testing, testers can use “drivers” as a replacement so that the testing can be continuous even when the application is not complete.
Here is an example to help you understand better:
Modules of clothing, clothes for men, clothes for women, tops, polo, and shirt are under development. Hence we can substitute them with related Drivers:
End-to-End Testing | Integration Testing | |
Purpose | Validates system behavior in real-world scenarios | Validates integration between components |
Scope | Broader in scope and cover the entire technology stack of the application | Interaction between different components/modules |
Cost | More expensive as it often requires more resources, including personnel, equipment, and testing environments. | Less expensive than end-to-end testing |
Testing stage | Performed at the end of the software development lifecycle before releases | After unit testing and before end-to-end testing |
Technique | Black-box testing, often uses User Acceptance Testing (UAT) | White-box testing, often uses API testing
|
Read More: What is Software Testing? Full Guide
With their differences in scope, focuses and approaches, these two types of testing can not be used interchangeably. End-to-End Testing and Integration Testing are complementary in the sense that they provide different levels of testing.
By performing Integration Testing first, any issues related to the interaction between different components can be identified, ensuring that the system functions as a whole, without any integration bottlenecks. End-to-End Testing then helps check if the software meets the requirements and specifications in real-world scenarios.
Both types of testing have a high level of complexity with the involvement of various modules, APIs, and systems, which makes them fine candidates for test automation.
While manual tests still remain necessary, they are not fully exhaustive. When it comes to large or complex systems, it may not be possible to execute every test case and cover all potential scenarios. Another challenge is providing a stable environment for end-to-end/integration testing. Humans are prone to making mistakes and it takes only one wrong click to derail a testing scenario.
Automated testing platforms can be leveraged to compensate for these limitations, ensuring more accurate, efficient, and stable E2E and integration tests.
Katalon is a comprehensive software quality management platform that supports a wide range of testing types. Katalon enables UI and functional automated testing for web, API, desktop, and mobile applications, all in one platform.
Below highlight some of the features that help simplify automated integration and end-to-end testing.
Writing code simulating user journeys typically requires programming, coding, and VBA (Visual Basic for Applications) knowledge, which can be a scary endeavor for people not familiar at all with software development.
Katalon's record-and-playback enables translating complex testing scenarios into simple, repeatable steps. Both technical and non-technical testers can design tests by interacting with the UI just like a regular user, the Recorder watches and records all your actions so that you can focus on creating the user journey itself.
Katalon provides robust support for API testing, including the ability to test GraphQL, REST, and SOAP APIs. Its integrations with GraphQL tools like Postman, Swagger, and SoapUI allow you to import existing API specifications and test your new API schema along with legacy API assets on one platform.
Read more: What is GraphQL Testing? How To Test GraphQL APIs?
Compatibility testing across various devices, browsers, and OSs can be challenging, especially when it comes to setting up physical environments to execute tests. This process can be laborious and delay the entire testing project.
With Katalon, you can easily run tests on local and cloud browsers, devices, and operating systems in parallel, ensuring comprehensive test coverage.
Test maintenance is one of E2E testing's most daunting tasks. Larger regression test suites, extended test flows, and constant UI changes can make maintenance a time-consuming responsibility.
Following the page object design model, Katalon provides a centralized repository for not only designing but also managing your test cases and their artifacts. All UI elements, objects, and locators are stored across tests in an object repository. When your UI changes, clicks are all it takes to get your automation scripts up and running again.
Test cases replicating real user scenarios can become unstable due to the complex nature of usage scenarios. Failed tests prevent testers from gaining valuable insights as the root causes may not reflect the AUT’s real performance.
Katalon supports the self-healing mechanism to tackle the issue of broken locators during execution. When the default locator fails, new and more maintainable ones are automatically produced for the same object to avoid flakiness when the web UI changes.