Test Case Design Techniques in Software Testing

Test case design is an essential part of software testing. It involves establishing a group of conditions or variables to verify the proper functioning of a software application or system. Efficient test case design helps ensure thorough testing of the software's features, which helps find bugs and enhance software quality.

In this guide, we’ll walk you through the basics of test case design techniques in software testing and how to write test cases for AI-based automated testing tools.

What is Test Case Design?

Test case design refers to a structured and sequential list of action items that attempt to verify a specific feature. At the heart of a test case design is a sequence of steps describing actions to be performed, the test data to be used, and an expected response for each action performed. 

You should write tests to cover the business, functional, and technical requirements. For adequate test coverage, you can refer to the requirements artifacts, whether they’re written in the form of user stories or technical design documents. The test case template and level of detail required will vary depending on the organization, type of software delivery project, and or the test management tool used. 

The Objective of Writing Test Cases

• Tests should help assess the specific functionality of a software application.
• Tests should document a sequence of steps to be executed, which can be helpful for reference when a software bug is found in the application.
• To identify issues in user experience and gaps in design at the early stages.

Standard Test Case Format

The test case template that you use in your organization may vary slightly, but here are the basic components of a standard test case:

• Test Case ID - usually auto-generated by the test management system
• Description of the test scenario
• Prerequisites
• Test steps (including expected results, description, and test data)
• Actual results for each test step
• Overall status - either pass or fail

Advantages of Test Case Design Techniques

Implementing test case design techniques offers a structured approach to software testing and numerous advantages. 

Here are some key advantages of test case design techniques:

• Guarantees comprehensive coverage.
• Detects defects more effectively than ad-hoc test cases.
• Provides reproducible tests with detailed descriptions of order and content.
• Standardizes the process, making it independent of individual testers.
• Ensures that test specifications are transferable and maintainable.
• Simplifies planning and managing the test process by splitting it into clear, manageable blocks.
• Helps identify complex scenarios and generate effective test data.
• Ensures that all software requirements are met.

Test case design techniques in software testing support faster, more efficient testing, reduce costs and increase software reliability.

Types of Test Case Design Techniques

Different types of test case design techniques address various testing needs and approaches. They ensure thorough coverage and effective evaluation of software functionality.

Exploratory vs Scripted Testing

There are two main approaches to test case design: exploratory testing vs scripted testing. In a scripted approach, test cases are designed in advance. In the exploratory approach, they are created on the fly. 

Exploratory testing allows testers to be creative when performing the test. Scripted tests are easier to replicate and are good candidates for automation. The idea is that automating scripted tests frees up testers to perform exploratory testing manually.

Example of the Test Steps from a Scripted Test:

• Testing without entering any username and password
• Test it only with the username
• Test it only with a password.
• Username with the wrong password
• Password with the wrong username
• The right username and the right password
• Cancel after entering username and password.
• Enter a long username and password that exceeds the set limit of characters.
• Try copying/pasting it in the password text box.
• After successfully signing out, try the “Back” option in your browser. Check whether it takes you to the “signed-in” page.

Black-box vs White-box Testing

The distinction between black-box versus white-box testing is based on how much of the application’s internal details are considered when designing test cases. Black-box testing, also known as specification-based or responsibility-based testing, disregards how the software was architected and simply designs test cases based on the system's specified external behavior or how the user perceives it. This approach aligns well with techniques such as behavior-driven testing, which also focuses on the system's behavior from the user's perspective.

White-box testing, also known as glass-box, structured, or implementation-based testing, designs test cases based on what we know about the system’s implementation, i.e., the code.

Knowing some important information about the implementation can actually help in black-box testing, which is sometimes called gray-box testing. For example, if the implementation of a sort operation uses an algorithm to sort lists shorter than 1000 items and another to sort lists longer than 1000 items, we can add more meaningful test cases to verify the correctness of both algorithms.

Use Case Testing

Use case testing is straightforward in principle: we base our test cases on the use cases. It is used for system testing (i.e., testing the system as a whole). For example, the main success scenario can be one test case, while each variation (due to extensions) can form another test case. However, use cases do not specify the exact data entered into the system. Instead, it might say something like “user enters his data into the system”. Therefore, the tester has to choose data by considering equivalence partitions and boundary values. Combining these often results in one use case, producing many test cases. 

Since exhaustive testing is impossible, your test plan needs to be efficient and focus on higher-priority use cases. One way to do this is to implement a scripted approach to testing high-priority test cases while exploratory testing lower-priority areas of concern that may emerge during testing.

How to Write Test Cases: Expert Tips

Writing effective test cases is crucial for ensuring that your software is thoroughly tested and functions as expected. Here, we'll explore the essential components of a well-written test case, best practices for creating them, and tips for ensuring that your test cases are clear, concise, and comprehensive.

Identification and classification:

• Each test case should have an ID and title so that it’s easily referenced in the future
• Indicate the system, subsystem, or module being tested so that it can be categorized for reporting and analysis purposes.

Instructions:

• Tell the tester precisely what to do, step by step.
• Testers should have all the information needed to run the test and only need to refer to the test case documentation provided.

Expected result:

• Cite expected results and provide them to the tester.
• Report test failure if the expected results are not produced. Be clear when comparing the expected results to the actual results.

Cleanup (when needed):

• Inform the tester how to restart/recover in the event of failure.

Best Practices for Writing Test Cases

1. Align with requirements: First, understand the requirements & while writing test cases do not assume any requirements on your own. Raise questions that are unclear in requirement or misleading or incomplete. Feel free to ask your business analyst or client questions. Don’t ask developers about this. Before designing the test cases, figure out all application features and ensure that the test case should cover all functionality mentioned in the requirement document. Use a traceability matrix to make sure that no requirements are left untested. 
2. Avoid redundancies: Plan your scope of testing to prevent repeating duplicate test cases. Generic test cases should be collected & combined in the test suite, which helps to minimize the effort of writing standard common test cases every time and can be used over the project life cycle.
3. Prioritize tests: Assign a priority to each test case. Select the test case priority depending on the business impact of the feature, component, or product. As you plan your test executions, pick high-priority test cases first, then medium, and then lastly low-priority test cases.
4. Group tests properly for reporting: End users or clients are always interested in reports, so test cases should be grouped properly (PhaseI, II wise, Module wise, Sprint wise, or User story wise if Agile methodology) so the end user will learn about the Quality of the product based on test case execution (number of test cases Passed/Failed).
5. Write clearly and succinctly: Your test cases should be simple and easy to understand. Avoid writing explanations like essays. Keep to the point. Be mindful of the input data your tests use since your test cases should validate the range of input data. Also, check how the system behaves in normal and abnormal conditions.
6. Be practical: Concentrate on real life scenarios that are likely to be faced by end users. To make sure that defects are verified, log bugs appropriately and provide evidence they’re fixed. Remember, every test case may or may not have defect linked, but each defect should have test case linked.

Test Case Design Techniques for AI-Based Tests

According to the World Quality Report 2021-2022, organizations are increasingly demanding AI/ML-based test automation techniques. To implement AI-based testing, test strategy and test design skills (32%) and understanding of AI implications on business processes (36%) are seen as some of the highest areas where skills are lacking to implement AI for test automation.

Extent to which artificial intelligence changes the skills needed from QA and test professionals - World Quality Report 2021-2022

One of the most important skills in designing AI-based tests is knowing how and when to incorporate verifications.

Importance of Verifications 

A verification is a step inside a test, a boolean expression that checks to see if the application is working as expected. It is a piece of logic that verifies whether a bug exists or not. A test without verifications is merely a set of steps, so verification allows the test to be considered passed or failed. 

Verifications are even more crucial for AI-based tests that dynamically keep up to date since non-verification steps can change. So, verifications in your test ensure that the test stays true to its original intent while machine learning autonomously heals other steps.

When to Add Verifications to Your Test

Make sure to add a verification whenever you run into these scenarios:

• Page Load: Is there a step that involves redirection to a new page? If so, this should be a verification.
• Element Update: As a consequence of a test step, is there any change to the element on the page? For example, a welcome banner is displayed after logging into an app. A verification should be added to ensure the banner is displayed.
• Application Logic: If the code has some internal logic. For example, the application has a validation to check if a required field is filled out correctly. There should be a verification to ensure that the validation doesn’t get triggered by any other action.

‍Conclusion

• Test case design involves a structured and sequential set of actions to verify a specific feature.
• Implementing different types of test case design techniques enhances software testing quality and efficiency.
• Standardization makes the testing process independent of individual testers and ensures transferable and maintainable test specifications.
• The advantages of test case design techniques include thorough coverage and effective defect detection.