End-to-end testing, also known as E2E testing, is a methodology used for ensuring that applications behave as expected and that the flow of data is maintained for all kinds of user tasks and processes. This type of testing approach starts from the end user’s perspective and simulates a real-world scenario. For example, on a sign-up form, you can expect a user to perform one or more of these actions:
- Enter a blank email and password
- Enter a valid email and password
- Enter an invalid email and password
- Click a sign-up button
You can use end-to-end testing to verify that all these actions work as a user might expect.
End-to-end testing may sound comprehensive, but there are many other testing methods that you should use with it to create a robust continuous integration practice. Some other testing types you should consider:
- Unit testing makes sure that every single component in a system works as expected.
- Functional testing makes sure that the system gives the correct output for a particular input.
- Integration testing combines the individual software modules and tests them together as a group.
These types of tests are different than end-to-end testing, which focuses on the complete user workflow.
Why is end-to-end testing important?
End-to-end testing has been widely adopted because it:
- Helps teams expand their test coverage by adding more detailed test cases than other testing methods like unit and functional testing.
- Ensures the application performs correctly by running the test cases based on the end user’s behavior.
- Helps release teams reduce the time to market by allowing them to automate critical user paths.
- Reduces the overall cost of building and maintaining software by decreasing the time it takes to test software.
- Helps predictably and reliably detect bugs.
End-to-end testing appeals to a multi-disciplinary group that includes developers, testers, managers, and users. Developers benefit because they can offload most of the testing and quality assurance to the QA team, freeing the devs up to work on adding features to the application. It is easier for testers to write end-to-end tests because they are based on the user’s behavior, which can be observed during usability testing and documented in tickets. End-to-end testing makes it simpler to catch problems before releasing the software to end users. By identifying the importance of a workflow to the real-world user, end-to-end testing helps managers prioritize tasks in the development backlog.
End-to-end testing also improves the user experience. Especially for applications requiring a lot of user interaction, like web, desktop, and mobile apps, user expectations are the basis for the test cases.
Challenges of end-to-end testing
End-to-end testing is a great way to test software, but it comes with some challenges too. Challenges present themselves because end-to-end testing:
- Is time-consuming.
- Must be designed to reproduce real-world scenarios.
- Requires a good understanding of user goals.
End-to-end testing can be time-consuming because it takes a complete understanding of the product to write test cases. A user can follow many paths in a large software product, and it’s rarely worthwhile to test each of them. Instead, companies often use unit tests, snapshot tests, and integrations tests more often, and use end-to-end tests for the highest priority user workflows.
Difficult to design tests
Because end-to-end tests simulate the real-world behavior of users, there are many components to consider while designing these tests.
For example, you can run a web application on many browsers, and each browser has different specifications. This means you have to write tests that are specific to these browsers. This daunting task can lead to budget overruns. In test-driven development, where you’re looking for quick feedback on the code, relying on end-to-end tests isn’t a good approach.
Understanding user goals
Users aren’t looking for features: they’re looking to solve their specific problems. End-to-end testing should focus on how effectively the app solves its users’ issues.
The problem is that not all development teams have a detailed understanding of user intentions. So, they must deploy methods early on during software development to gather users’ perspectives on the functioning of the software. User research can be quite costly, so teams often rely on the same set of users to work as “beta testers” for an application.
How to implement end-to-end testing
Now that you know that you want to add some end-to-end tests to your development process, where do you start? Designing the end-to-end test cases is a good first step. Then, you can begin by testing manually until it makes sense to start automating your end-to-end tests.
Designing end-to-end test cases
Because end-to-end testing requires some preparation, it’s good to be familiar with the steps involved in implementing these tests. Here are the steps for a typical end-to-end testing procedure:
- Review the requirements to validate the end-to-end testing results.
- Set up test environments and requirements.
- Define all the processes of systems and subsystems.
- Describe the roles and responsibilities of each system and the subsystems.
- Outline the testing tools and frameworks.
- List the requirements for designing test cases.
- List the input and output data for each system.
Once you have gone through these steps, you can implement end-to-end testing.
Manual end-to-end testing
Manual testing is performed by a human tester directly interacting with the testing software. These testers can quickly learn what works and what doesn’t when writing a test plan. Manual testing helps identify test cases and helps testers uncover hidden user interaction paths in the system. That gives testers the information they need to start automating these test cases in the future. The test plans and test cases built manually can become automated tests.
There are two ways to do manual testing: horizontal and vertical.
Horizontal end-to-end testing covers the entire application. It requires software development teams to have well-defined workflows and established test environments. A single test workflow can span multiple subsystems. A plan for simultaneously testing UI, a database, and email integration is an example of a horizontal end-to-end test.
Vertical end-to-end testing breaks down the application into layers that you can test individually. Vertical end-to-end tests often precede their horizontal counterparts because of this granularity. For example, performing a vertical end-to-end test with user interface subsystems allows you to easily identify and fix bugs.
Automated end-to-end testing
As your project grows, performing all end-to-end testing manually will become less manageable. This is especially true of testing user interfaces, because an action in a user interface can lead to many other actions. This complexity makes testing automation essential. End-to-end tests can help automate user-interaction testing, saving valuable time.
Once you’ve decided on the test cases, you can write them as code and integrate them with an automated testing tool. For example, you can use a CI/CD pipeline to automate the end-to-end testing of software.
With the speed at which software acquires new features, automating software testing is the only viable option. Automation enables you to catch bugs quicker because the entire code base is automatically checked against the test cases each time you add new code.
This article reviewed what end-to-end testing is and described its benefits and challenges. Implementation techniques for end-to-end testing were covered, including horizontal testing, vertical testing, and the distinction between manual and automatic testing.
Manual testing is a great place to start, and a good foundation for building automated tests. Automation not only saves time and prevents complications, it frees your team to do what they do best - develop applications.