How to Ensure 100% Test Case Coverage of Requirements (2024)

Creating comprehensive test scenarios and cases that ensure 100% coverage of requirements is a multi-faceted process involving several key strategies.

The objective is to make sure that every aspect of a software requirement is thoroughly tested, including positive, negative, and edge cases.

Let’s delve into a structured approach to achieve this, illustrated with an example and supported by insights from industry sources.

1. Understanding the Requirements

Begin by clearly understanding the software requirement. For instance, if the requirement is for a user authentication system, it should include details like

• accepting username and password,
• validating credentials,
• handling incorrect inputs, etc.

2. Developing User Personas

Creating user personas helps envision how different users might interact with the software. This step is crucial in developing relevant test scenarios and cases.

For our example, personas might include

• a first-time user,
• a returning user with correct credentials,
• a user who has forgotten their password.

3. Identifying Test Scenarios

Test scenarios are high-level ideas about what to test. For the authentication system, scenarios could include:

• Successful login
• Login with incorrect credentials
• Login with empty credentials
• Password recovery process

4. Outlining Test Cases

Test cases are specific actions to be performed in testing. For each scenario, develop test cases covering positive, negative, and edge cases.

For example:

• Positive Test Case 1: Enter valid username and password > Expect successful login.
• Negative Test Case 1: Enter invalid username > Expect error message.
• Negative Test Case 2: Enter invalid password > Expect error message.
• Edge Case 1: Enter maximum length allowed for username and password > Expect successful login or appropriate error message.
• Edge Case 2: Leave username and password fields empty > Expect error message.
• Edge Case 3: Exceed the limits of characters allowed for username and password fields > Expect error message.

5. Incorporating Different Coverage Metrics

Use various coverage metrics like statement coverage, branch coverage, and path coverage. These metrics ensure different aspects of code and functionalities are tested.

• Statement Coverage

Ensuring every line of code in the login functionality is executed at least once.

• Branch Coverage

Testing all branches of conditional logic in the login process.

It focuses on ensuring that each possible branch from each decision point in the code is executed at least once. This type of coverage is crucial for testing the decision-making logic of an application.

In the login process, consider the following decision points:

Username and Password Validation:

• If both fields are filled, proceed to credential verification.
• If either field is empty, display an error message.

Credential Verification:

• If the username and password combination is correct, proceed to successful login.
• If the combination is incorrect, display an error message.

In branch coverage, you would create test cases to cover each of these decision branches:

Test cases for Username and Password validation

• Enter both username and password > Expect the system to proceed to credential verification.
• Enter only username or password > Expect an error message.

Test cases for credential verification

• Enter valid username and password > Expect successful login and redirection.
• Enter invalid username or password > Expect an error message.

Branch coverage ensures that all the decision branches in the code are tested, but it does not necessarily cover all possible paths as path coverage does. For example, it might not cover the scenario where both the username and password fields are empty, as this would be a specific path rather than a decision branch.

While branch coverage is less comprehensive than path coverage, it is more focused and often more feasible for large applications where testing every possible path can be impractical. Branch coverage is particularly useful for ensuring the robustness of the application’s logic and can significantly reduce the number of bugs related to decision-making processes.

• Path Coverage

Testing all possible paths in the login process, including different sequences of user actions.

Let’s take the example of a login process to illustrate path coverage. Assume the login process involves entering a username and password, and it has the following logical components:

1. Input validation that hecks if the username and password fields are filled.
2. Credential verification which verifies if the username and password combination is correct.
3. Error handling which displays appropriate error messages.
4. Successful login that redirects to the homepage upon successful login.

Now, consider the following paths:

Path 1. Successful Login

• User enters the correct username and password.
• The system verifies credentials.
• The user is redirected to the homepage.

Path 2. Incorrect Credentials

• User enters incorrect username or password.
• The system checks credentials and finds a mismatch.
• An error message is displayed.

Path 3. Missing Username

• User enters a password but leaves the username blank.
• The input validation fails.
• An error message for missing username is displayed.

Path 4. Missing Password

• User enters a username but leaves the password blank.
• The input validation fails.
• An error message for missing password is displayed.

Path 5. Both Fields Empty

• User does not enter username or password.
• The input validation fails.
• An error message for missing credentials is displayed.

In path coverage testing, each of these paths would be executed at least once. This helps to ensure that all possible scenarios, including edge cases, are tested, thereby increasing the likelihood of identifying potential bugs or issues in the login process.

6. Requirement-Based Coverage

Align test cases with the software’s requirements to ensure that all functionalities and components outlined in the Software Requirement Specification (SRS) are covered.

7. Risk-Based Coverage

Prioritize testing based on the risk analysis. High-risk areas, like security aspects of the login system, should be given more attention.

8. Boundary and Equivalence Testing

Test the boundaries and equivalence classes of input data. For example, test the minimum and maximum lengths of username and password fields.

9. Error Guessing

Use expertise and intuition to guess potential error-prone areas.

10. Using Test Case Management Tools

Use tools like TestCaseLab for managing and organizing test cases. This aids in tracking progress, identifying gaps, and ensuring all test cases are up to date and aligned with current requirements.

11. Regular Review and Updates

Regularly review and update test cases to accommodate changes in requirements and feedback from testing results. This is vital in agile environments where requirements may evolve.

12. Monitoring and Tracking

Monitor all test cases to avoid duplications and ensure comprehensive coverage. Use metrics and feedback to refine the testing process continuously.

Here’s a comprehensive approach based on insights from various sources:

Test Coverage Matrix

Creating a test coverage matrix helps in organizing and ensuring thorough testing. This includes listing all devices, browsers, OSes, and mapping these to the requirements. The matrix should be dynamic, evolving with updates in devices, browsers, and user expectations. Moreover, setting clear goals for test coverage percentages is important for guiding the testing process​​.

Best Practices in Test Case Writing

Effective test cases are the backbone of thorough testing. They should be clear, concise, and written from the user’s perspective. Include all necessary details like prerequisites, test steps, expected results, and post-conditions. Regularly reviewing and updating test cases ensures they align with current requirements and functionalities. Using test case templates, as provided by tools like TestCaseLab, can enhance consistency and efficiency​​​​.

Prioritizing Test Cases

Test cases should be prioritized based on factors like risk, version, and cost. For example, in an e-commerce application, a test case for verifying the correct calculation of sales tax would be prioritized over a less critical feature like button color​​.

Automating Testing Processes

Automation is key in handling the volume of tests needed for thorough coverage, especially within tight deadlines. Automated testing, particularly parallel testing, allows for more tests to be executed quickly. Cloud-based testing services can facilitate this process by providing access to a wide range of browsers and devices for testing​​.

Test Plan and Test Suite

Understand the difference between a Test Plan and a Test Suite. A Test Plan is an up-to-date document that accompanies the team throughout the project, focusing on what types of tests should be performed and when. In contrast, a Test Suite is a collection of test cases used for different types of testing, like Regression, UAT, and Sanity testing​​.

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