How to Find Out Edge Cases ??

As software testers, we always seek ways to ensure that the application under test performs reliably in all scenarios.

While testing common user flows is important, edge cases often reveal the most critical bugs, especially those that could compromise the product's functionality or user experience.

Let’s explore edge cases, why they matter, and how to identify them when planning tests and writing test cases.

?? What Are Edge Cases?

Edge cases are scenarios that occur at the extreme limits of your system’s capabilities. They represent unusual or rare conditions that users might encounter. This could involve extreme data inputs, rare sequences of events, or interactions at the boundaries of system performance.

Think about scenarios that may not occur often but could significantly impact the user experience when they do happen.

? For example, imagine testing a payment form allowing users to enter their credit card information. An edge case could be testing what happens when a user enters the longest valid credit card number or when the user enters a mix of invalid characters and symbols. These aren’t typical use cases but are still critical to ensure the system can handle unexpected inputs gracefully.

?? Why Are Edge Cases Important?

Ignoring edge cases can lead to the following:

? Unstable user experiences

Users might encounter crashes or security vulnerabilities when a system doesn’t handle rare scenarios well.

? Security risks

Some edge cases expose vulnerabilities that could be exploited by malicious users, leading to security breaches.

? Poor performance

Edge cases can test the limits of system performance, revealing hidden bottlenecks.

?? How to Find Out Edge Cases?

The key to identifying edge cases is shifting your mindset from focusing only on the typical user behavior to considering unexpected, extreme, or unusual scenarios.

Here are a few tips on how to start thinking about edge cases:

1?? Look at the limits of input fields, numeric ranges, and system thresholds.?

• What happens when you exceed, meet, or undercut these boundaries??
• If a field requires a username between 6 and 20 characters, what happens if a user tries to enter a 21-character name?
• Or a blank username?

2?? Step away from the conventional user flows.?

Consider behaviors that users might unintentionally or intentionally perform that could break the system. This might involve using unsupported browsers, trying complex combinations of actions, or doing things in the “wrong” order.

3?? Think about different types of users and their behavior.?

• How would an experienced user interact with the system versus a novice??

• What about users with accessibility needs or those in areas with poor network connectivity?

Now that you understand how to think about edge cases, let’s focus on practical steps to uncover these scenarios during the test-planning and case-writing phases.????

? Start by reading the product requirements and identifying potential ambiguities or edge conditions. Ask questions like:

? What’s the minimum and maximum value allowed for each field?

?How should the system behave if an invalid input is given?

?Are there performance expectations under high load?

? Challenge assumptions made in the requirements and probe for details on how the system should behave in less common scenarios.

? Use boundary value analysis. This is a structured approach to test at the boundaries of input ranges. Identify minimum, maximum, and middle values, as well as values just outside of the valid range. For instance, if the system accepts ages between 18 and 60, test with values such as 17, 18, 59, 60, and 61.

? Perform negative testing. Intentionally test the system with invalid or unexpected inputs.

?What happens when a user enters special characters into a field meant for numbers?

?What if they leave fields blank or try to upload an unusually large file? Negative testing helps uncover how well the system handles errors.

? Consider time-based edge cases. If your application involves any time-based features, such as scheduling or expiration dates, test across different time zones, daylight saving changes, and leap years. Testing these time-related edge cases ensures the system works consistently regardless of the time-related context.

? Leverage exploratory testing.?

In exploratory testing, you’re free to creatively interact with the application, allowing for the discovery of edge cases you might not have anticipated when writing test cases. As you explore the system, think about how users might behave unexpectedly.

? Talk to developers, product managers, and even end-users for insights. Often, developers can suggest edge cases based on the system’s architecture or known limitations, and users can provide real-world scenarios you may not have considered.

Take a proactive approach to edge case testing, and you’ll be better equipped to catch critical bugs before they reach your users.

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