We are living in a digitally enabled world where software systems play a critical role. Whether you are at an airport or railway station, bank, grocery store, or any other place, you can easily witness how software systems help in facilitating business processes. Based on our dependency, you can easily understand the amount of disruption a software failure can cause in our daily lives. This is where software testing comes in. It ensures that the software is robust enough to handle real-life use cases. To understand the amount of testing, we use a parameter known as “test coverage”. In this blog, we will explore what is test coverage in software testing, why it is critical, and best practices to achieve high test coverage.
What is test coverage?
Test coverage is a key software testing metric that evaluates the extent to which a software application’s code is tested by a given set of test cases. Represented as a percentage, it helps identify untested areas in the program, ensuring comprehensive validation and minimizing potential risks.
Test Coverage = Number of lines of code tested X 100
Total number of lines of code
What is the purpose of test coverage?
- It helps in identifying the gaps in the testing. Since it highlights the area, which is not covered under the executed test suite, it provides information about areas under risks.
- It helps in improving software quality as QA teams create additional test cases to cover the uncovered code of an application.
- It helps in identifying redundant test cases that are not contributing to coverage.
Test Coverage vs. Code Coverage
Both test coverage and code coverage are equally important to ensure the quality of an application, however, both are different.
Code coverage is related to unit testing. It is used to measure the percentage of lines and execution paths in the code. It ensures that every line or block of code is executed at least once by the developers. It ensures that all branches in conditional statements as well as all possible execution paths are tested.
Contrary to this, test coverage is all about validating features and functionalities. It is performed by QA team during functional and integration testing.
Test Coverage Techniques
Statement Coverage: It ensures that every line of code in a program is executed at least once during testing. It helps confirm that the code behaves as expected. However, one limitation is that it only verifies whether statements run but doesn’t account for all possible conditions—such as whether loops reach their termination points or how the program handles false conditions.
Branch Coverage: In a program, branching occurs when execution can follow multiple paths based on conditions or decisions made during runtime. Essentially, it involves jumping from one decision point to another. Branch coverage ensures that every possible path—both true and false conditions—is tested, unlike statement coverage, which only checks if statements are executed. However, one drawback is that it overlooks branches within Boolean expressions caused by short-circuit operators.
Path Coverage: Path testing is a software testing technique that analyzes a program’s source code to identify and execute every possible path from start to finish. It ensures thorough test coverage by verifying all statements and branches. One of its key benefits is eliminating redundant test cases, leading to more efficient testing. However, its complexity and time-consuming nature make it challenging to implement, especially for large applications such as ERPs.
Condition Coverage: It ensures that every condition in the code is tested for both possible outcomes—true and false. This method requires at least two test cases per condition to verify both scenarios. Its key advantage is that it evaluates each condition independently, leading to more precise and thorough testing.
Boundary Value Coverage: It focuses on testing values at the edges of equivalence classes, as errors are more likely to occur at boundaries rather than in the middle of an input range. This method is effective for detecting data handling, validation, and boundary-related issues. Its simplicity and ease of automation make it a widely used approach. However, a key limitation is that it does not account for dependencies between multiple inputs.
Product Coverage: It involves testing a software solution from the perspective of the product, focusing on specific areas. It emphasizes the user’s viewpoint. The scope can be expanded using tools like prioritization charts, automation, and checklists.
Risk Coverage: It involves thoroughly evaluating all software-related risks and rigorously testing the application. This process includes identifying and assessing potential risks, even low-probability scenarios that could significantly impact the software. By doing so, it ensures that all possible dangers associated with the software under development are addressed through testing.
Requirements Coverage: It ensures that the final product includes all features which are committed and meets the customer’s specified needs. It involves checking which software requirements have been tested and identifying any that haven’t, ensuring nothing important is overlooked.
Best practices for test coverage
Set Realistic Goals: The objective of the test coverage should be set realistically based on project requirements and risk levels.
Incorporate test automation: Use test automation tools to automate repetitive tasks, execute repeatable tests and reuse test cases. Manual testing should focus on exploratory testing.
Avoid over testing: Executing a greater number of test cases doesn’t guarantee 100 percent coverage. Avoid redundant test cases and focus on more critical test cases based on impact.
Continuously improve: As the application evolves, keep on adding new test cases to maintain effective coverage.
