Introduction
Code coverage is a key metric in software testing that measures the percentage of source code executed during test runs. While high code coverage may give confidence that much of the code has been tested, it doesn’t always provide a full picture. Many types of test cases are not included in code coverage, leaving potential risks undiscovered. In this blog, we will explore the types of test cases that are typically not reflected in code coverage and why understanding these gaps is crucial for effective testing.
1. Non-Functional Test Cases
a. Performance Testing
Performance tests focus on how efficiently a system performs under various loads, measuring factors like response time, throughput, and resource usage. These tests are designed to simulate real-world scenarios where a system is stressed under heavy usage, but they don’t always execute specific code paths, especially if performance bottlenecks are external (e.g., network latency).
For example, testing how quickly a web page loads under heavy traffic doesn’t necessarily touch upon code coverage, as it evaluates system behavior rather than the execution of specific code blocks.
b. Security Testing
Security testing aims to uncover vulnerabilities like SQL injection, cross-site scripting (XSS), and authentication loopholes. Although security testing probes the system for weaknesses, it often does not contribute to code coverage because it targets potential threats instead of code execution paths.
c. Usability Testing
Usability tests focus on the overall user experience, ensuring the application is user-friendly and intuitive. Code coverage tools do not track user interface interactions or feedback on usability, so these tests typically fall outside the scope of code coverage metrics.
d. Scalability Testing
Scalability testing evaluates how well a system performs as the workload increases, but it doesn’t contribute to code coverage. The focus is on system performance under increasing loads, rather than verifying whether individual functions or methods are executed.
2. Business Logic or High-Level Workflow Tests
Business logic tests often assess the entire system’s functionality by simulating real-world workflows. These tests may include end-to-end processes that involve multiple components working together. However, such tests do not always cover every individual function or code path, especially if they skip over certain parts of the logic.
For instance, an end-to-end test might ensure that a customer can successfully complete a purchase on an e-commerce site, but it won’t necessarily execute every code path related to error handling, alternate payment methods, or non-critical functions.
3. Error Handling and Exception Test Cases
Tests that focus on error handling and exceptions are often not fully reflected in code coverage. These cases involve testing how the system responds when things go wrong, such as invalid input, network failures, or database crashes. Since these events are triggered only under specific conditions, the corresponding code paths are rarely executed in regular tests.
For example, if an application is supposed to handle a “division by zero” error gracefully, but your test cases don’t simulate this condition, the code that handles this exception won’t be counted in the code coverage metrics.
4. Boundary and Edge Case Tests
Boundary and edge case tests check how the system behaves at the limits of acceptable input values. These tests ensure that the system handles both minimum and maximum input values correctly but may not contribute significantly to code coverage, particularly if the code that manages these conditions is abstracted or generalized.
For instance, testing the behavior of an application when receiving the largest possible input value might not cover a wide range of code paths but is still critical for verifying robustness.
5. Configuration-Specific Test Cases
Many test cases are designed to assess how software performs in specific configurations or environments, such as different hardware setups, operating systems, or network conditions. These tests are critical to ensure compatibility and reliability, but they may not trigger code paths within the software itself.
For example, testing how well an application runs on different versions of Windows or Linux may not affect the internal logic, leaving code coverage unchanged.
6. Manual Test Cases
Manual testing remains a significant part of the software testing lifecycle, especially for exploratory or usability testing. However, manual test cases are not typically included in code coverage, as they are often more focused on discovering unexpected bugs or issues rather than systematically executing specific code paths.
A manual tester might uncover a bug that an automated test missed, but this discovery won’t affect code coverage metrics, as the code path where the bug occurs may not have been executed during the automated tests.
7. Tests Involving Third-Party Libraries or APIs
Applications often rely on third-party libraries or external APIs to function. While testing these integrations is essential, they usually don’t contribute to code coverage, as the code executed belongs to external systems.
For example, testing whether an API call successfully retrieves data from a remote server does not affect your internal application’s code coverage, even though it is a critical part of the system.
8. Visual and Accessibility Testing
Visual testing ensures that elements on a web page or application appear as expected across different devices, browsers, or screen resolutions. Accessibility testing verifies that the software is usable by people with disabilities, ensuring compatibility with screen readers, keyboard navigation, and more. Both types of testing are crucial for user experience but don’t directly interact with code paths, making them invisible to code coverage metrics.
9. Untested Dependencies
Sometimes, your application depends on libraries or frameworks that you didn’t write, but these dependencies are critical for the application to function. If the third-party code isn’t covered by your tests, it won’t show up in your code coverage report, even though untested dependencies can be a significant risk.
For example, if your software relies on a third-party authentication service, failing to test its integration or behavior under certain conditions won’t appear in code coverage.
10. UI Automation Test Cases
Many UI automation test cases involve interacting with the application through its graphical interface. While these tests are useful for ensuring that the UI works as expected, they may not trigger all underlying code paths, especially in parts of the application that handle backend processing or data management.
Conclusion
While code coverage is a valuable metric in software testing, it doesn’t always capture the full scope of your testing efforts. Non-functional tests, manual test cases, error handling, and third-party library tests are just some examples of test cases that are not included in code coverage. To ensure your software is thoroughly tested, it’s important to go beyond code coverage metrics and adopt a more holistic testing strategy that includes these critical areas.