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Edge Cases in Software Testing Explained! (From A-Z)

During the process of testing, there is a good chance that things will not always go according to plan and run smoothly. And it’s possible that some of the cases we encounter will be related to software testing. Examples include the edge and corner cases, both of which are typical subjects for discussion in the context of software testing. Even though these two situations are very different from one another, they are frequently compared to one another as though they were the same.

Edge Cases in Software Testing

When it comes to testing software, an “edge case” is a problem that arises when the operating parameters are pushed to their absolute limits (either the maximum or the minimum). Users are only marginally likely to run into edge cases. There are some edge cases that occur quite frequently and can take place in either software applications or website design. Among them are the following:

• Application crashes are the most frequent case of which there is no obvious cause.

• It typically takes five seconds or longer for a section of an application or website to load in this case.

 Audio issue: Occasionally, after the video screen has been closed, the background audio won’t play.

However, it is important to note that this particular scenario does not always occur in all users; as a result, it is expected of us in quality assurance that we will always be ready with solutions for any issues that may arise in the applications or websites that we develop.

Typical Edge Cases

This is a bit of an oxymoron because the very definition of a “edge case” in software testing is that it does not occur frequently and does not affect a large number of users. However, there are still a number of edge cases that tend to occur fairly frequently across a variety of apps and websites in general. Some examples of these are as follows:

  • Crashes. The crashing of an application without a clear cause or a path that is easily reproducible is one of the edge cases that occurs most frequently. Most of the time, the developer would be able to determine the cause simply by looking at the source code. However, as a tester, it’s possible that you won’t be able to easily replicate the error. 
  • Occasionally, a portion of the application or website will require an additional five seconds to load (regardless of network speed).
  • It sometimes happens that audio will continue to play in the background after a video screen has been closed.

There are some edge cases that are specific to the website or app that they manifest on. However, you might be able to find others on a wide variety of websites or mobile applications.

Finding edge cases

How does a quality assurance tester determine which test cases are considered edge cases, or how do they locate edge case defects? The best piece of guidance that can be given is to actively search for edge cases. In a nutshell, testers make use of their imagination and capacity for critical thinking in order to discover edge case defects during any test cycle, whether it be regression, functional, or at any point in the development cycle. The reality is that testers constantly look for edge cases, or at least as many as they have time to focus on, but the goal remains the same. Once the application system has been connected and developed to the point where an end-to-end test can be performed, the testers should plan some time to find those hidden and frequently obscure edge test cases.

An experienced QA tester has the innate ability to discover the areas of the application that are most likely to fail, particularly as they continue to test a system. In addition, they will be better equipped to identify edge cases the more they understand the customer workflow. Testers frequently discover common edge cases in places they are already familiar with. Imagine integration points as places where the application either saves data to the database or processes data that has been received from messages. Other than that, how else can they locate edge cases? First, consider what the end user is trying to accomplish with the application, and then think about how those functions can be accomplished without following the expected path. Better yet, how can they use that function to make the application carry out a scenario that is completely different from what was anticipated?

Say, for instance, that your application is responsible for processing income tax forms for people living in the United States, France, China, and the United Kingdom. The result is that there are four unique collections of tax rules and computations, one for each country plus additional rules for each state or area. Now, let’s say you go in and edit the tax rules for the United States, and then you manage to create an entirely new country with an entirely new set of rules, while still making use of the dataset of customer accounts that already exists. You configure the system so that all user accounts will send their dividends to the offshore bank account you specify. Despite the fact that this is an extreme example, you may have just discovered a significant security edge test case if the test is successful.

There are a lot of edge test cases that are either less significant or smaller. Continuing with our demonstration of how security works, let’s say that you are testing the workflow for a user to log in in order to access their tax account. Imagine that you are a business in the United States whose job requires you to keep the regulations governing taxes current with the most recent amendments. You are only permitted to view the account for the United States. You are able to log in with the correct username, but you have entered the wrong password. The software gives an error message about an invalid login attempt. The following set of questions may help explain how to locate edge case defects in this example:

  • Is it possible to get around the login screen by doing a double click on the window’s frame?
  • Can you access a website without logging in if you quickly click several times on the screen’s edge or outside the login window?
  • Do you have access as a system administrator or superuser after logging in?
  • Do you now have access and functions to all accounts if you are logged in as an admin?

How to test edge cases in software testing

The development of tests for edge cases in software testing is complementary to the development of other types of tests. The key difference is that you have to make room in your schedule for quality assurance testers to exercise their creativity and imagination in order to test alternatives to the happy path. You should give the execution of edge case tests a higher priority and incorporate them into your regression tests. If time is an issue, however, you can delegate a member of the quality assurance team to run the tests after the regression has been completed. Edge cases are an essential component that must be included in an overall quality assurance testing plan, regardless of where you perform your testing.

Testing in an edge case scenario can be challenging. The process of conducting fringe testing requires patience, in-depth thought, originality, and exploration. However, keep in mind that edge test cases represent what users do to manipulate your application, whether intentionally or not, which could give them unauthorized access to data and systems if you don’t test for them. Consider a defect known as an edge case, in which it is extremely difficult to scroll without inadvertently pressing a button. This is not the only reason why this is important. Although there was no malice intended, the customer will have a negative experience, which will decrease their satisfaction and loyalty to the brand. Imagine yourself in the shoes of a user or a malicious hacker; this is the best way to test edge cases and find bugs. Patience is required for fringe testing, but it is absolutely necessary for the success of both an application and your company to ensure that edge case tests are developed and carried out.

If you are unable to test edge cases internally, you can select a software testing partner in whom you have complete faith to perform this task in an effective and safe manner. To ensure that organisations deliver exceptional digital experiences to their customers, Applause offers software testing services and solutions that span the entirety of the software testing life cycle. Applause’s global community of digital experts can find defects within the scope you define, on the devices you prioritize, and validate that apps deliver a secure and consistent experience for users. This is applicable to edge case testing. In the end, businesses conduct testing on applications in order to provide customers with high-quality experiences. Testers have a responsibility to ensure that an application is capable of performing not only the typical workflow but also any and all edge test cases that, if they were executed, would cause harm to the application or expose sensitive customer data and systems. The time spent on testing extreme cases is time well spent for both the company and its customers.

Should Edge Cases Be Fixed?

It is dependent on a number of different aspects. How common is this problem, and how significant is its impact on the functionality of the system? For instance, a bug that only occurs 1% of the time might appear to be quite uncommon. On the other hand, if the bug prevents a user from checking out of their shopping cart and the platform has 500,000 users, this could have a significant impact on the platform’s revenue. Some teams are under the impression that the fact that a bug only occurs in edge cases means that it never needs to be fixed. However, this perspective isn’t always the most useful. Problems can be caused by something even if it does not affect a large number of users or occur very frequently. This does not mean, however, that the problem cannot occur. It is typically worthwhile to make the adjustment, particularly if it is a simple one. This will not only make the software better, but it will also reduce the likelihood that your customer service team will need to respond to complaints from users who are negatively impacted by the change.

The user experience of a mobile application or website can cause users to stop using it. Even if the bug does not have a significant impact on functionality, it may still be making the user’s experience more frustrating overall. It is also important to keep in mind that a bug has an effect on more people than just the ones who come into contact with it. In today’s world, information can travel at lightning speed, and a lot of people are more than happy to air their grievances on publicly accessible social media accounts. Even if a bug does not affect the vast majority of your users, a user who is negatively impacted by it may still tweet about it. Because of this, anyone who reads the post will form a negative impression of the product you sell.

When is it okay to chase Edge Cases?

If you are employed by a company that has already successfully launched a product, your time may be split between two different endeavours: the elimination of bugs and edge cases, as well as the incorporation of new features. It is more of an 80/20 split, with new feature integration taking up 80% of the time, rather than a 50/50 split evenly distributed between the two. During the product development process, it is not the time to go hunting for edge cases, and this is especially true if you are trying to release the product. The vast majority of people have the misconception that the software must be flawless before it can be distributed to the general public. However, the reality is that you will never release a product if you test it to ensure that it is flawless. This may sound counterintuitive.

Therefore, if you work for a large company that strives for product perfection (like Apple), your greatest strength may be discovering edge-cases. You will be revered as the greatest thing since sliced bread, and champagne will pour from the heavens. You’ll typically be told that you’re wasting time in other places.


How to Find and Test Edge Cases. (2021, September 28). Applause. Retrieved December 20, 2022, from https://www.applause.com/blog/how-to-find-test-edge-cases

Blogs, D. (2022, January 7). Learn More! What are Edge Cases and Corner Cases? Medium. Retrieved December 20, 2022, from https://medium.com/@dojobox.id/learn-more-what-are-edge-cases-and-corner-cases-f1e0321ed3ea

Cajic, D. (2022, June 10). Chasing Edge Cases. Medium. Retrieved December 20, 2022, from https://blog.devgenius.io/chasing-edge-cases-3f03a0197128

Silverstein, W. (2020, November 16). What Are Edge Cases in Software Testing? – 2022 Edition – Mindful QA. Mindful QA. Retrieved December 20, 2022, from https://www.mindfulqa.com/edge-cases/