Best Practices for Writing Effective Test Cases

Writing effective test cases is crucial for ensuring software quality and reliability. A well-structured test case not only helps identify defects but also ensures that the software behaves as expected under various conditions. Below are best practices and guidelines for writing clear, concise, reusable, and comprehensive test cases. 

What is a Test Case?

A tester uses a specific set of conditions or variables to determine whether a system, software application, or one of its features works as intended.

Example: You are testing the Login pop-up of the leading E-commerce platforms. You’ll need several test cases to check if all features of this page are working smoothly.  

Steps to ask yourself 3 questions Before You Write Effective Test Case: 

1. Choose your approach to test case design: your approach influences your test case design. Are you doing black box testing (you don’t have access to the code source) or white box testing (you have access to the source code)? Are you doing manual testing or automation testing?  
2. Choose your tool/framework for test case authoring: are you using frameworks or tools to test? What level of expertise do these tools/frameworks require?  
3. Choose your execution environment: this ties up closely with your test strategy. Do you want to execute across browsers/OS/environments? How can you incorporate that into your test script? 

Once all those 3 questions have been answered, you can start the test case design and eventually test authoring. It’s safe to say that 80% of writing a test case belongs to the planning and designing part, and only 20% is actually scripting. Writing effective test case design is key to achieving good test coverage. 

How to Design a Effective Test Case? 

Write effective test cases – when we don’t need to understand the details of how the software works, we focus on checking if it meets user expectations. We explore the system to come up with test ideas. However, this approach can result in limited testing, as we might overlook features with unusual behaviour. 

In that case, here are some techniques for you to design your test cases: 

• Equivalence Class Testing: In Equivalence Class Testing, you divide input data into groups and treat all values in each group the same way.

Example: For an age input field that accepts ages from 18 to 65, you can choose 3 values for 3 equivalence classes and test with one value from each group. That means you have 3 test cases. You can choose: 

17 (below 18-65 range) 
30 (within 18-65 range) 
70 (above 18-65 range) 

• Boundary Value Analysis: this is a more granular version of equivalence class testing. Here you test values at the edges of input ranges to find errors at the boundaries. 

Example: For an age input that accepts values from 18 to 65, you choose up to 6 values to test (which means you have 6 test cases):  

17 (just below) 
18 (at the boundary) 
19 (just above) 
64 (just below) 
65 (at the boundary) 
66 (just above) 

• Decision Table Testing: you use a table to test different combinations of input conditions and their corresponding actions or results.

Example: Here’s a decision table for a simple loan approval system. Specifically, the system approves or denies loans based on two conditions: the applicant’s credit score and the applicant’s income. From this table, you can write 6 test cases.

How to write effective Test Case 

Standard Test Case Format

We use a test case to check if a feature or function in an app works properly. It has details like conditions, inputs, steps, and expected results. A good test case makes testing easy to understand, repeat, and complete. 

Components of a Standard Effective Test Case 

Test Case ID: Give a unique ID like “TC001” or “LOGIN_001” to every test case. This helps in tracking. 

Test Case Description: Write a short description of what the test case tests. For example, “Test login with correct username and password.” 

Preconditions: Mention any setup needed before starting.  

Test Data: List the inputs for the test. Like, “Username: test_user, Password: Test@123.” 

Test Steps: Write step-by-step actions for the test. Keep it clear and simple. 

Expected Results: Describe what should happen if everything works. For example, “User logs in and sees the dashboard.” 

Actual Results: Note what happened during the test. This is written after running the test. 

Pass/Fail Status: Mark if the test passed or failed by comparing expected and actual results. 

Remarks/Comments: Add any extra info like problems faced, defect IDs, or special notes. 

Example of a Standard Test Case Format 

How to write effective test cases: A step-by-step guide

If I explain to you in just a two-line summary of how to write an effective manual test case, it would be:

1. Identify the feature or functionality you wish to test.
2. Next, create a list of test cases that define specific actions to validate the functionality. Now, let’s explore the detailed steps for writing test cases. 

Step 1 – Test Case ID: 

Additionally, assign a unique identifier to the test case to help the tester easily recall and identify it in the future.

Example: TC-01: Verify Login Functionality for a User 

Step 2 – Test Case Description:

We will describe the test case, explaining its purpose and expected behaviour. For example: 

Test Case Description: Logging into the application 
Given: A valid username and password 
When: User enters credentials on the login page 
Then: User logs in successfully and is directed to the home page. 

Step 3 – Pre-Conditions: 

We will document any pre-conditions needed for the test, such as specific configuration settings. 

Step 4 – Test Steps: 

We will document the detailed steps necessary to execute the test case. This includes deciding which actions should be taken to perform the test and also possible data inputs. 

Example steps for our login test: 

1. Launch the login application under test. 
2. Enter a valid username and password in the appropriate fields. 
3. Click the ‘Login’ button. 
4. Verify that the user has been successfully logged in. 
5. Log out and check if the user is logged out of the system. 

Step 5 – Test Data: 

We will define any necessary test data. For example, if the test case needs to test that login fails for incorrect credentials, then test data would be a set of incorrect usernames/passwords. 

Step 6 – Expected Result: 

Next, we will provide the expected result of the test, which the tester aims to verify. For example, here are ways to define expected results:

1. A user should be able to enter a valid username and password and click the login button. 
2. The application should authenticate the user’s credentials and grant access to the application. 
3. The invalid user should not be able to enter the valid username and password; click the login button. 
4. The application should reject the user’s credentials and display an appropriate error message. 

Step 7 – Post Condition:

The tester is responsible for any cleanup after the test, including reverting settings and removing files created during the test. For example: 

1. Successful login with valid credentials. 
2. Error message for invalid credentials. 
3. Secure storage of user credentials. 
4. Correct redirection after login. 
5. Restricted access to pages without login. 
6. Protection against unauthorized data access. 

Step 8 – Actual Result: 

We will document the actual result of the test. This is the result the tester observed when running the test. Example: After entering the correct username and password, the user is successfully logged in and is presented with the welcome page. 

Step 9 – Status: 

The tester will report the status of the test. If the expected and actual results match, the test is said to have passed. The tester marks the test as failed if the results do not match.

Manual and automated test cases share some common elements, but when using automation, include these 6 key elements. Those are: preconditions, test steps, sync and wait, comments, debugging statements, and output statements. 

Best Practice for writing effective Test Case 

Follow key best practices to write effective test cases.

First, identify the purpose of the test case and determine exactly what needs to be tested.

Write the test case clearly and concisely, providing step-by-step instructions. Also, it is important to consider all possible scenarios and edge cases to ensure thorough testing. 

It is always to review and refine your test cases occasionally to maintain their quality over time. 

By following these best practices for writing effective test cases, we can increase the chances of spotting defects early in the software development process, ensuring optimal performance for end use. 

Benefits of writing high-quality and effective Test cases 

Indeed, writing effective test cases is important because it ensures high-quality software. Moreover, well-written test cases provide multiple benefits.

Let me narrow down to some essential facts here: 

1. Accurate Issue Identification: High-quality test cases ensure thorough testing and accurate identification of bugs. 
2. Better Test Coverage: Test cases evaluate different aspects of the software, identifying bugs before release. 
3. Improved Software Quality: Identifying issues early reduces repair costs and improves software reliability. 
4. Better Collaboration: High-quality test cases help stakeholders work together, improving communication and resources. 
5. Enhanced User Experience: Test cases improve the software’s usability, enhancing the end user’s experience. 

Conclusion

Writing effective test cases is a systematic process that requires attention to detail and clarity. By following these best practices—understanding requirements, structuring test cases properly, covering various scenarios, ensuring reusability, documenting results, and regularly reviewing your work—you will create a robust testing framework that enhances software quality. Implementing these guidelines will not only streamline your testing process but also contribute significantly to delivering high-quality software products that meet user expectations. 

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