What Is an Edge Case Testing? How To Find and Prioritize

June 12, 2024Kiruthika Devaraj
What Is an Edge Case Testing How To Find and Prioritize

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Edge case testing is software testing that verifies whether a system can handle extreme or out-of-ordinary scenarios considered unlikely to occur in normal usage. It helps ensure the system is robust and reliable and can handle unexpected situations gracefully. This blog post will explain what it is and why it’s so important.

What are edge test cases?

Case testing, also known as edge case testing, is a form of software testing that focuses on testing for exceptional behavior or conditions found at the boundaries of a program or system. So these unusual or rare scenarios occur at expected input or behavior boundaries. They are often the result of incorrect assumptions about how the software will be used and can result in unexpected or incorrect responses from the system. Edge cases are important to consider in the development process to ensure that the system can handle a wide range of inputs while continuing to produce expected outputs.

So, you know those times when you close a video(reels) on Instagram, but the sound keeps playing in the background for a few seconds? That’s a classic example of an edge case!

What is an edge test case example?

Let us look at a real-time example of an Edge case test case.

Scenario: Log in to a website

Test Data: Incorrect username or password when the ‘Log-in’ button is pressed

Expected Result: The user should not be able to log in, and an error message should be displayed.

This example explains: this is a test case designed to test the system’s response when incorrect username or password information is entered. The expected result of this test is that the user should not be able to log in. There will be an error message displayed. The tester can use this Edge Test Case to test the system’s functionality by entering any invalid input. This ensures the system is secure and the application provides the expected user experience.

Why are edge cases important to consider?

If you want to know why edge cases are legit important, you must learn some cool facts first!

  1. Edge cases can reveal flaws in a system or process that may not be apparent in typical scenarios. We can identify and address potential issues by considering edge cases before they become bigger problems.
  2. Edge cases often represent real-world scenarios that may occur infrequently but still have significant consequences if not properly addressed. Considering these scenarios, we can ensure our systems and processes are robust enough to handle them.
  3. Edge cases can also help us improve the user experience by identifying situations where users may encounter unexpected behavior or errors. Addressing these edge cases can make our systems more user-friendly and reduce user frustration.
  4. Edge cases can seriously affect patient safety or financial stability in some industries, such as healthcare or finance. Viewing these scenarios, we can ensure that our systems and processes are designed to minimize risk and protect those who rely on them.

Edge case testing and test automation

You should consider automating your edge case testing if you’re working with an application with a limited range of repeatable and controllable input values.

Test automation usually performs edge case testing to verify predetermined software outputs using automated tests. Automation testing ensures that a system meets the expected performance, quality, behavior, and configuration of the test case. Automated test scripts can detect problems that manual tests cannot identify. Teams often use automated testing to speed up test suites and to check edge cases on complex web applications and systems.

Here is a guide with in-depth discussions on dos and don’ts of automated testing.

Check out the guide

How to Find Edge Cases in Software Testing?

So, edge cases in software testing are scenarios outside the normal range of inputs and behaviors. They’re like the crazy outliers we must test for, just in case.

  • Sometimes, we must test things we did not expect or plan for. It’s like testing the quirky and rough things that could happen but probably won’t. You want to ensure the software can handle those roughest inputs and unexpected situations.
  • When testers have a lot of data to work with and think the tests might fail at the highest or lowest limits of the data, they use something called Boundary Value Analysis. This means we’re checking out the upper and lower limits of input data values because we reckon that’s where our test cases could go wrong. This technique works best when we’ve got a ton of test data.

Let’s say you’re testing a website that only allows for usernames with 6-12 characters. With boundary value analysis, you’d test the lower limit (6 characters), the exact limit (7 characters), and the upper limit (12 characters).

  • Next, there’s Equivalence Partitioning. This one’s about breaking up a huge dataset into smaller chunks. If we pass any random value from a chunk, we can assume that we have covered the chunk and don’t need to test everything in it separately.

Let’s say you’re testing a website that only allows usernames with alphanumeric characters. You could partition this into two equivalence classes: all alphabetic characters and all numerical characters. You can then test one value from each of the two classes to ensure the website accepts numbers and letters.

  • A team of testers can do edge case testing manually, or specialized tools can automate it.

How to do edge case testing?

Edge case testing is an important part of software testing that involves testing the system’s extreme or boundary conditions, often overlooked during regular testing. This testing can be done both manual and automated ways.

The Manual Way:

  • Identify the edge cases: The first step is to identify the edge cases for your application. This can be done by analyzing the requirements and specifications of the system.
  • Create test cases: Once you have identified the edge cases, create test cases that cover these scenarios. You should include inputs at or beyond the limits of what is expected in these test cases.
  • Execute test cases: Execute each test case manually and observe how the system behaves under these conditions.
  • Record results: Record the results of each test case, including any issues or defects found during testing.

The Automated Way :

1. Identify potential edge cases: The first step is to identify the potential edge cases in the system. This can be done by analyzing the requirements, user stories, and use cases.

2. Develop test scenarios: Once the potential edge cases have been identified, the next step is to develop test scenarios that cover these cases. These scenarios should be designed to test the system’s behavior under extreme conditions.

3. Use automation tools: Automation tools such as Testsigma, Selenium, and Appium can automate the execution of these test scenarios. These tools can simulate user interactions with the system and verify its behavior under different conditions.

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4. Analyze results: After executing the automated tests, it is important to analyze the results to identify any issues or defects that may have been uncovered. This analysis can help improve the system’s quality by identifying areas that need improvement or further testing.

Why do edge case testing before release?

You might wonder about this WHY question! I will explain why we do edge case testing before the release.

Before product release, edge case testing is important to check how the system behaves in extreme conditions. Unexpected behavior of a system can frustrate users and make them abandon the product.

Edge case testing involves testing the system’s boundaries by entering values beyond normal use limits, such as providing an unusually large or negative input. This can identify and eliminate bugs or unexpected behavior in extreme use cases. Edge case testing can help provide customers with a smooth and seamless user experience.

How to prioritize edge cases?

Prioritizing edge cases can be challenging because these are rare and unique scenarios. However, it is important to prioritize these cases as they can seriously impact the product’s user experience and overall functionality. One approach to prioritizing edge cases is considering their potential impact on user safety, legal compliance, and business goals. Also, gathering feedback from users and stakeholders can help identify which edge cases are most important to address.

Tips for edge case testing in your development

Are you ready to grasp some tips to do this testing? Here you go:

1. Think from the perspective of your users – how would they use the app, what path would they follow, if they had to do something unexpected what would it be?

2. Think of unlikely scenarios in terms of app usage and failures – like what if the battery died, what if a call came while app was being used, what if a notification came up.

3. Always have the mindset – if you can think it, the user can do it. So, never assume and always test for all possible user paths.


So, there you have it – by finding, prioritizing, and testing edge cases, you can improve the overall quality of your product and increase customer satisfaction. So, don’t overlook the edge cases – they might be the key to your product’s success!

Frequently Asked Questions

What are edge and corner cases in testing?

Developers perform edge case tests at the application’s or software’s boundary values. They also perform corner case tests at the intersection of multiple boundary values of the application or software.

What is the difference between base case and edge case?

We use base cases as the basis for solving more complex cases. Base cases are the simplest and most fundamental cases of a problem. Edge cases are specific, unusual cases of a problem that will cause the algorithm or system to break.

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