Did you know that every high-quality app and software suite you’ve ever used has been through end-to-end (E2E) testing? Why? It’s because the developers and testers must make sure the software is successfully doing what the developers designed it to do. As such, end-to-end testing is a crucial part of quality control in the software industry.

Exploring End-to-End Testing 

So, what is end-to-end testing? When testers do end-to-end testing on an application, they test it in its entirety. That is why it’s called end-to-end testing. It tests the application from beginning to end, finding out how users will experience it. If problems show up during the evaluation, developers must resolve them.  

End-to-end tests are also known as “user acceptance tests (UATs),” “smoke tests,” “browser tests,” or even “UI tests.” However, even though some people call end-to-end tests UI tests, that’s not truly accurate. 

How Does End-to-End Testing Work?

During the end-to-end test, the testers will open the software in a specialized browser. Once they’ve done that, they will test the program through interaction. No stone is left unturned. Testers check the APIs, third-party integrations, the codebase, the server, the network, and the browser (including its compatibility with the software). They also test any involved hardware. 

What Are the Different Types of End-to-End Testing? 

There are two primary types of end-to-end testing, horizontal and vertical. Read more about them below.

Horizontal End-to-End Testing 

This kind of end-to-end testing evaluates an application in its entirety. To prepare for horizontal testing, you need to know you are testing a whole workflow across numerous different applications. And since the system and sub-systems you use for the testing are important, you will need to test these first independently. 

There are several benefits to choosing horizontal end-to-end testing. One of these is its thoroughness and breadth. It also centers on user-friendliness. You get an exact idea of what the real user experience will be. If the software should interact with other applications, testers must also test this interactivity. 

When a business uses software, testers may also focus on how it will interact with the target businesses’ database and network infrastructure. Testers always do horizontal testing as the final step of the release cycle. 

Vertical End-to-End Testing 

With vertical end-to-end testing, testers first split the application into its component layers, where they test each layer by itself. The layers are tested sequentially in their hierarchical order. Some of the layers may be API requests and UI database calls. 

Vertical testing has some advantages. For one, it’s appropriate for software where safety is especially crucial, and it has excellent code coverage. You may also find the testing process faster than you would with horizontal end-to-end testing. 

With vertical testing, the software is typically tested along with UI layers, API integration, and network infrastructure. This type of testing is more granular in its approach than horizontal testing, although both types of testing must address all details in the end. 

A major difference between vertical and horizontal testing is that testers can do horizontal testing more independently. That means that the developer can have the horizontal end-to-end testing done without bringing in other stakeholders. Vertical testing, in turn, involves collaborating with other stakeholders, such as potential product owners. 

End-to-End Testing Metrics

End-to-end testing is hugely dependent on quality testing metrics and the proceeding feedback cycle. There are hundreds of different testing metrics, all bespoke to the product and industry. However, conceptually they all follow the same general trains of thought, providing data for systems and systems analysts to assess. Let’s take a look at some of the broader types of test metrics: 

Weekly Test Progress

The weekly test progress metric gives testers progress data when it comes to weekly testing. It tells them the number of developed tests, as well as the success (pass/fail) rate. It also communicates the unexecuted and executed test rate. 

Test Case Preparation Status

This status measures the number of prepared test cases, and it sets this against the number of test cases that have been planned. 

Test Environment Availability 

The metric shows the amount of time that testers have for testing a specific environment versus the time actually spent testing every day. 

Defects Status and Details 

This metric tells testers what defects were detected during testing. It indicates how many open and closed defects there are in the application. 

End-to-End Use Cases

As we learned earlier, apps and software need end-to-end testing before developers distribute them to consumers. Without it, the developers won’t know if their apps will work as intended. 

  • End-to-end testing should be done on finished software products before developers distribute them. This lets the developers know that the entire software system is working as it should. It’s an important part of quality assurance. 
  • This testing will also be done if there are problems later detected in the software. When this happens, testers will test the system and analyze the data they find to determine the problem and how to fix it.

Other Kinds of Tests

Before building an end-to-end testing scenario, there are other kinds of tests that should be done. These include the two other tests of what testers refer to as the testing pyramid: unit tests and integration tests.   

Unit tests

Unit tests evaluate the tiniest code units, such as functions. This test will ensure that any coding such as text strings or numerical values used for buttons, forms, or links are properly functioning. If any function has external dependencies, you will have to use a different process. 

Integration tests

Integration tests evaluate how two separate entities work together. This is useful if two different developers worked on different modules that must operate together to perform a function. This kind of test takes longer than function tests. 

For obvious reasons, end-to-end tests take much longer to complete than unit tests and integration tests. If testers detect problems during an end-to-end test, it takes a lot of time and effort to isolate the specific areas. As end-to-end tests have the broadest scope of all the tests, they are extremely difficult to create. 


End-to-end testing is an essential process for any software development. Before software hits the market, it’s important that all functions are operating properly and efficiently to heighten the user experience.