End-to-End Testing vs. Integration Testing: When to Use What?

The software development lifecycle (SDLC) is a process that results in a successful platform release. Testing is a crucial component that ensures digital products’ quality and readiness to be accessed by real users. The approaches to qualifying software performance are numerous, and they are distributed according to the project’s structure, from testing individual elements to testing the entire application.

End-to-end and integration testing approach the product as a whole system. While their main goal is to ensure users receive an error-free platform, the instruments and means these testing methods use suggest they differ. Let’s see what end-to-end and integration testing offer and why they are two core software-checking methodologies.

What Is End-to-End Testing?

End-to-end (E2E) testing refers to the procedure of examining software performance from beginning to end. This approach offers a unique opportunity to examine the platform from the user’s point of view. Quality assurance (QA) teams performing E2E checking start at the beginning of the visitor’s journey and finish when the interaction cycle is over.

The simulations of real users’ actions help to determine whether the platform functions as intended and its components form a holistic system. Other performance aspects like user-friendliness, responsiveness, and reliability are also covered.

Test Coverage

End-to-end testing covers all aspects of the platform. This comprehensive methodology offers to test the software not only at the stage of separate features but also at the interaction of all modules. Moreover, it looks at the product as a system, examining all its components, interfaces, and integrations.

From the user’s point of view, the workflow might seem straightforward: to open the application, log in, and see the content. But even such a simple customer journey implies numerous questions for QA specialists.

The specifics of E2E testing coverage are that there are many options for paths and journeys that the user can take. So, the first challenge testers face is mapping out and prioritizing testing scenarios.

End-to-End Testing Advantages

Conducting end-to-end tests offers numerous benefits, including:

• Real user experience issues identification. If other testing methods, like unit testing, reveal errors only from the internal perspective, E2E checks software performance from the external perspective, namely the user’s side. This helps to uncover issues that cannot be spotted without applying end-user experience.
• Early integration problem detection. The extensive test coverage allows testers to examine whether the system’s separate parts communicate with each other, from the APIs to the UI/UX design elements. It happens before the product’s release and can prevent real users from experiencing the issues.
• Redundant test reduction. E2E testing is conducted at the higher structure level: user journeys, workflows, and scenarios. So, there is no need to examine every component to see if the problem lies in the integration. Once it is fixed, testers don’t review separate modules again.

Methods and Instruments of End-to-End Testing

An end-to-end test can be executed by following two different methods: horizontal and vertical. The horizontal model applies to checking the product on multiple applications simultaneously from the beginning to the end of user interaction. It ensures software performance is at the expected level and all user requirements are met.

Vertical end-to-end testing takes place at one application and examines every system layer. Testers go from one level to another, ensuring their functionality. This is a more thorough method, and it allows developers to know where the issue appeared after the test. In horizontal methodology, QA teams only identify that there is an issue.

Testers use test automation tools and user interface testing tools in E2E testing. The criteria for choosing the right instrument are based on available integrations with programming languages and frameworks, ease of usage, and pricing value. Some popular tools are Selenium, Cypress, Appium, Cucumber, Testim, and Avo Assure.

Real-Case Scenario for E2E Testing

Let’s look at an example of end-to-end testing.

The case examines the journey when the customer enters the platform, explores it, and successfully purchases the product. In this scenario, the following aspects require testing:

1. 1. Navigation to the website
2. 2. Correct search options and filters
3. 3. Displaying accurate results in the cart
4. 4. Payment validation process
5. 5. Sending a confirmation message
6. 6. Displaying correct billing and product information details in the receipt
7. 7. Listing customer’s order in the order history in the user account

Examining all these steps gives an overview of the product selection and purchasing processes.

What Is Integration Testing?

This testing type examines the proper performance of different modules when combined. It is higher than unit testing, which focuses on exposing errors about a certain unit’s functionality. In integration testing, interfaces between the modules that coexist in the dependency are checked.

QA specialists investigate the ability of separate units to communicate with each other. They test the interaction of the elements.

Test Coverage

Integration tests cover fewer aspects of the software than end-to-end testing. They mainly focus on checking a service call for one or more dependencies. For instance, integration testing can examine whether the confirmation email triggered by a successful purchase displays the correct information.

In this testing type, QA teams check several components that work seamlessly together rather than the system as a whole.

Integration Testing Advantages

These are the pros of applying integration testing:

• Integration error identification. Different developers might create separate software elements with their own understanding of the functionality. Integration testing helps reveal whether the units coexist and communicate properly with each other.
• Seamless data flow insurance. An integration test also focuses on checking interfaces. It examines whether one interface transfers correct information to the other, ensuring the data flow is seamless and accurate.

Methods and Instruments of Integration Testing

Integration testing offers different approaches to its execution. There are two main methods QA teams follow: incremental and non-incremental testing. The first represents checking the platform from one element to another logically. For example, when examining an application, the testing will go from Login > Dashboard > Search > Card

> Order Placement > Logout.

In the non-incremental method, testers check all the modules at once after they have been investigated in unit testing. This approach is time and budget-efficient.

You can also use a hybrid method, which combines the features of each approach. Every method applies diverse techniques, such as top-down, bottom-up, and big bang.

Integration testing is performed with programs that simulate the missing module and help reproduce the data flow scenario. These programs are drivers and stubs. Testers use the following helpful instruments for integration checking: Selenium, Jasmine, Pytest, Mockito, LDRA, Steam, and Junit.

Real-Case Scenario for Integration Testing

Imagine a fitness application with these features: Sign-in> Onboarding > Subscription plans > Payment > Access to the app’s features. With integration testing, QA experts ensure that:

1. 1. The flow proceeds seamlessly.
2. 2. After every successful action, the user is redirected to the next logical step.
3. 3. The data from the onboarding stage is correctly displayed in the application after the subscription purchase.
4. 4. The system identifies the purchase as successful and opens access to the app.

Integration type of testing ensures that every step logically follows the next steps.

End-to-End Testing vs Integration Testing

Find the core differences between end-to-end and integration testing in the table below:

When Is It Better to Use End-to-End Testing?

E2E testing is not always suited for conducting. Since it is a time and resource-consuming practice, you should estimate your project specifics to determine whether to implement this type of testing. If the following factors are inherent in your case, use end-to-end testing.

• Critical user flows. If your application has numerous essential user journeys, it is better to test the whole system thoroughly. Such flows include user registration, adding products to a cart, conducting payments, delivering orders, and similar.
• High-level systems. End-to-end testing checks every level of the entire system. This type of testing ensures maximum coverage for applications that contain many and various layers.

When Is It Better to Use Integration Testing?

Integration testing aims to check communication between specific modules. It is well suited for applying after unit testing. Here are also reasons why integration testing is the best choice.

• Early error detection. Integration testing exposes issues at the early development stage, lowering the risk of building a bug-ridden application.
• Focus on certain functions. This testing technique thoroughly examines communication between particular modules, while in E2E testing software, it is checked as a whole system. If you aim to investigate a specific feature, integration testing will help.

End-to-End and Integration Testing: Combination of the Best Practices

Choosing a suitable testing method depends on the specifics of your projects and goals. However, experts recommend combining their best practices instead of strictly selecting one type over the other.
For example, integration testing techniques should prevail if your software has numerous integrations. If your product is based on complex interfaces, E2E techniques should dominate.

Conclusion

End-to-end and integration testing both offer the possibility of ensuring software quality and performance. While the E2E type examines the entire system’s functionality from the user’s perspective, integration focuses on checking communication between different modules.

QA teams should combine two testing techniques to achieve comprehensive results. If you need expertise on which testing type to choose for your project, contact White Test Lab. Our professional testing team will offer you the best software testing solutions.