End-to-end (E2E) testing is a methodology created to prevent many scenarios a user can get during the use of the application. It is also a great way to test different use cases, and predict different results on each screen, layer, and application component. The main objective of end-to-end (E2E) testing is to mimic the end customer's experience while confirming the data integration and reliability of the system and all of its components. These days, software systems are intricately linked together and have several subsystems, and If one of the subsystems fails, the entire software system may fail. Hence, this article covers the basics you need to know about E2E testing.
Understanding one of the most critical tests for software development and how it can help the developers and the application.
To have a dependable and effective program, it is necessary to ensure that everything flows as intended, preventing defects from occurring when a user accesses the system. E2E testing comes into play at this point. In this article, we will discuss how this testing technique is often used in an agile environment like Fetchly, how many other testing methodologies are used, and how it helps the integrity of an application.
What is E2E testing?
End-to-end testing, also known as E2E testing, is a technique that assesses the application from start to finish. The goal is to test the entire application workflow to ensure that every element, feature, piece of data, interaction, and integrated piece works as expected.
The main idea of an end-to-end test is to simulate a real user experience scenario with clicks, scrolls, drags-and-drops, and so on to validate the integrity of the functionalities and data. For example, on a login form, the E2E test performs as a real user and tests:
- An invalid and valid email
- Invalid and valid password
- Submit the data
- The behavior for a successful and a failed login
E2E testing is robust and can help find many bugs and increase the quality of the application. Other tests and end-to-end testing create a robust and continuous integration environment. We will discuss more of them in the next part of the article.
As mentioned before, E2E testing is made to improve and ensure the quality and robustness of the whole application. Along with E2E testing, two other methods of app testing are applied here at Fetchly:
Unit testing: As the name suggests, it tests and ensures that every system component works and behaves as expected, as a single unit. This is a significant step to follow in Fetchly, irrespective of the order of the pyramid, as it checks for errors found in a line of code at the earlier stage to save time when there is a need to rectify mistakes later.
- Integration testing: This test aims to check how individual software pieces inside the application interact and behave as a group. And in an agile environment like Fetchly, integration testing gives the flexibility to make necessary changes.
These three tests, when combined, enable Fetchly team members to ensure that every single component of the project works by itself, when connecting with others, and when interacting with the whole system (just like a gear).
From the picture of the pyramid above, you can take note of the shape it takes and the order it follows.
The unit tests should be done more frequently, followed by integration and end-to-end testing. That’s because the tests at the base of the pyramid have automation, creation, and execution costs much smaller than the ones on the top. Unit and integration tests can also reduce the number of E2E testing, thereby reducing costs when created and replicated efficiently. It also helps with validating business rules and small cases.
Horizontal and vertical testing
If we look at the pyramid displayed above, we can classify E2E testing into two types: horizontal and vertical.
This kind of testing covers the entire application. It aims to check if every component in that scenario works appropriately as expected. A horizontal test (from the Senior QA to the Junior QA here at Fetchly) can cover and verify multiple subsystems. A UI, database, form integration, and performance test can be considered horizontal testing.
Unlike horizontal testing, this method breaks down the application into layers and verifies them individually ( from colleagues working on the same project) to ensure the quality of each layer. The components are tested from start to finish. This is also an easier way to find bugs in each layer, and it’s crucial to note that this test is commonly done before the horizontal.
As the application grows, it becomes necessary to carry out automated end-to-end testing because managing all the tests manually becomes challenging. This is especially important for UI, as one action can lead to multiple results, while with automated tests, it's much easier to catch bugs and fix them. Here are a few tools that help with automating tests:
Katalon Studio: This easy-to-use software helps with E2E testing for mobile and web.
Cypress: It is a very popular NodeJS library used for testing web applications.
End-to-end tests are a great tool that can improve a lot of the application quality, but it comes with a few challenges, such as;
- It needs to have a clear idea of what the user's goal is.
- It costs a lot of time, as it tests a lot of workflows, data, and functionalities.
- It needs to test the application in the production environment to have the best results possible, and chances are that the environment will only sometimes be available for it.
End-to-end (E2E) testing is essential if you want an application without bugs and the best user experience possible. In Fetchly, this helps the production of the application to simulate many different user scenarios and predict different results, therefore ensuring the quality and consistency of the system.
*This is not the official Fetchly opinion but the opinion of the writer who is employed by Fetchly*