End-to-End Testing vs Integration Testing: Key differences

Software testing and its importance in the development process

As a software evaluation process, testing provides development teams with methods to verify that their product performs as expected and does what it was designed to do. Although many consider testing as just another “formality” in software building, it is actually a critical stage that allows companies to ensure their customers will get a high-quality product. By getting rid of defects and bugs, you can spare your users many problems that would negatively affect their satisfaction and harm the image of your company.

Understanding End-to-End Testing and E2E Tests

End-to-End (E2E) testing is a comprehensive testing methodology that allows QA specialists, testers, and developers to make sure their product behaves as intended and all the features work properly. The approach is described as end-to-end as it covers the entire application and all its components–from one end to the other. The purpose of such testing is to simulate the behavior of real users and check how your app works in real-life scenarios.

Scope of End-to-End Testing

E2E testing should cover the following aspects:

• Performance and scalability: Software should be able to handle many users, different volumes of data, and heavy workloads.
• Functionality: Testing should allow you to check if all the features of an app behave as they should and that your software works well with other software and systems.
• Usability: E2E testing should involve checking the app’s UI and mechanism to ensure the software is intuitive and easy to use for users.
• Security: An important part of testing is verifying that the software is safe and there are no problems related to unauthorized access, encryption, or data breaches.

Key objectives and benefits of End-to-End Testing

The most important objectives of E2E testing are:

• Making sure that your software works according to its functional requirements.
• Checking whether the app behaves as it should in various conditions and under different workloads.
• Ensuring that your app can’t be compromised in terms of security such as data breaches.
• Verifying that your app is user-friendly and your customers can use it without difficulties.

There is also a number of benefits that can come with E2E testing:

• It allows you to minimize the risk of bugs that would otherwise find their way into the production environment.
• As a tester, you can use E2E testing to contribute to the increased quality and stability of your software.
• E2E testing, due to its comprehensive nature, can reveal weaknesses in the usability area.
• It can help make the software more secure and improve its performance as it allows you to find problem areas as well as bottlenecks.

Example of E2E testing

As an example of an End-to-End Testing process, let’s consider testing of a hotel booking app:

1. First, a tester checks the sign-up and sign-in processes in the app to validate the registration and login features.
2. Second, the tester checks the search feature to verify that searching for hotels and filtering them works as it should.
3. Next, they make sure that it’s possible to select and book rooms and the correct booking information is shown to the user.
4. Then, the tester validates the payment processing feature, for example, by using a credit card as a payment method. They ensure that the process is secure and goes smoothly.
5. The tester verifies if the user receives the correct booking information. The information needs to match what the tester had selected before booking and paying for the room. Also, they make sure the app shows the room as unavailable now (since it’s been booked and paid for).
6. The tester verifies all the notifications and reservation updates a user might receive.
7. When the tester has finished checking the front end of the app, they make sure everything is also fine on the back end of the app (for example, updating room availability or payment handling).

Understanding Integration Testing

Integration testing is called so because it is a testing method that allows QA specialists and testers to make sure that different modules and components of software work well when they are combined and integrated together. It's sometimes confused with unit testing, however, integration testing and unit testing are two different types of testing. While unit testing focuses on individual units of code, the goal of integration testing is to find out if there are any problems or bugs that come from the integration of various software elements.

Scope of Integration Testing

Integration testing should cover such areas as:

• Verifying the interaction between components: Testing should let you make sure that various software modules work correctly together.
• Verifying that data is properly transmitted within the software ecosystem: Through integration testing, you can check if the data is carried from one place to another in an expected manner.
• Verifying appropriate error response: Testing should allow you to verify if the app correctly handles errors (for example, showing error messages and being stable in spite of erroneous data).

Key objectives and benefits of Integration Testing

The most essential objectives of integration testing are:

• Ensuring that various software modules and components work correctly together.
• Finding and fixing issues and bugs that result from such integration of software elements.
• Verifying that your application works as described in its software requirements.

Noteworthy benefits of integration testing include:

• It lets you identify integration problems early before users notice them in the production environment.
• It’s a great way to establish intricate relationships and dependencies between software modules.
• It allows you to make sure that your software remains scalable and reliable under a bigger load.
• It can save your company time and money.
• Given the involvement of different software modules and elements, integration testing requires greater collaboration between teams in your organization.

Example of Integration Testing

Let’s once again use the example of a hotel booking app to illustrate how integration testing might work.

Such an app can have the following modules:

• A user interface in which customers can look for hotels, read reviews, book rooms, and pay for them.
• A database that contains all the details and information about hotels.
• A payment mechanism that lets users pay for the rooms they book.

The integration process for such an app would involve:

1. Verifying that the internal search feature works as it should and displays correct and up-to-date data.
2. Checking if opening a window with the details of a specific hotel gets and shows proper data from the database.
3. Testing if the booking system works correctly.
4. Finding out that the payment processing, most likely integrated with a third-party payment service, works smoothly and without problems.
5. Checking if an email confirming the reservation is correctly sent out via a dedicated mailing system.

Key differences between End-to-End Testing vs Integration Testing

The scopes and purposes of e2e and integration testing types aren't the same. Each testing method focuses on different aspects of software and can take place at different stages of development. Below, you'll find a table with the most important things that differentiate end-to-end testing vs integration testing.

When to Use End-to-End Testing vs Integration Testing

You should use E2E testing when:

• Your application is complex and the risk of bugs appearing in different areas of the app is high.
• You have a lot of users and defects might affect multiple groups of customers.
• You’re developing an app that must be really reliable, so a banking app rather than a mobile game.
• Your software is used within a regulated industry, for example, finance.

You should use integration testing when:

• You use microservices architecture to build your software and you need to make sure those microservices work correctly together.
• Different teams in your organization create different modules of your software and you have to make sure the modules interact with each other as expected.
• You use a CI/CD pipeline to develop your app, so you can make integration testing a part of that pipeline.

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Best Practices for End-to-End Testing

When it comes to E2E testing, it’s always good for a tester to:

• Begin with a plan in which you define features to be tested, user scenarios, and the results that you expect.
• Use real-life scenarios that mimic the actions of real users.
• Automate the testing process.
• Add continuous monitoring to find new bugs.
• Do regression testing to ensure new features don’t break the existing ones.
• Invite stakeholders to the testing process to make sure you focus on the correct areas of your software.
• Prepare analyses of testing results.

Best Practices for Integration Testing

• Integration testing goes well when you as a QA specialist:
• Establish what the most important integration points are.
• Get a grasp on how various modules and components work together.
• Use well-prepared and purposefully limited data for integration testing.
• Automate the testing process.
• Keep on tracking issues related to integration.
• Collaborate with people from different teams that are responsible for different software components and modules.

Challenges and Considerations

When it comes to E2E testing, you might face several challenges and things to consider:

• E2E testing requires a testing environment that resembles that of production. Your team will need to dedicate time (which also means: money) to setting up such an environment.
• You’ll need to have real-life data for E2E tests. Such data may not be easy to obtain.
• E2E testing is time-consuming, so you’ll have to think about tools that will allow you to automate the whole process.
• Such testing is complex, as testers need to understand the tested system or application really well.

As for integration testing, remember the following:

• Integration testing is done in environments configured for specific module interactions.
• It requires the data that has been selected and prepared for such testing.
• It can take a lot of time, so think about test automation tools that can facilitate the process.
• Integration testing can be demanding because QA specialists need to understand a multitude of interdependencies and interactions between software components and modules.

Technologies and tools for End-to-End Testing and Integration Testing

There are technologies that you may find useful for both end-to-end and integration testing, they include:

• Test data management: An approach to handling test data in a consistent and accurate way.
• Test reports: Tracking and reporting bugs as well as the progress of testing. Test reports let you show the test results to other people on your team.
• CI/CD pipelines: Such pipelines allow you to automate the processes of testing and software deployment.

Popular tools used for E2E and Integration Testing in software development

You can find many tools that make end-to-end testing easier. The good and popular ones are:

• BugBug: An intuitive testing platform that provides you with quick and efficient E2E testing capabilities. Suitable for every tester, regardless of their professional experience.
• Selenium: An open-source solution that lets you automate E2E tests.
• TestComplete: A popular commercial testing utility. It can be used for various kinds of apps: desktop, mobile, and web-based ones.
• TestNG: A free yet powerful testing tool that has some sought-after features like annotating and reporting.

The differences between End-to-End Testing and Integration Testing

E2E testing is used for verifying software from start to finish while integration testing checks the interactions and interdependencies between software components. Integration tests are conducted at the early stages of the development cycle.

In turn, E2E tests usually take place later in the development process. Moreover, end to end testing requires real-life data and an environment that mimics the production environment whereas integration testing is based on limited, purposefully selected data, often verified in dedicated environments that may not resemble the production.

When to use E2E and Integration Testing

You can use E2E testing if you’re dealing with a complex app and the risk of having defects in different parts of the app is substantial. Also, E2E testing is required if your team is developing software that requires a high level of trustworthiness, for example, a banking app.

On the other hand, you can make use of integration testing if your app is built with multiple components or microservices and you need to check how they interact with each other. This type of testing is also appropriate for organizations that have many teams responsible for various modules of their software.

Remember that comprehensive testing is crucial for a successful software development process. It allows you to find bugs early before they are carried over into the production environment with the new code. The fewer defects your app has, the better the user experience–and from there the road to a positive image of your product and company is really short.

Happy (automated) testing!