Test Coverage Techniques Every Tester Must Know

Building software is helpful, but it is also prone to many errors. Software that has poor design doesn’t just ruin the user experience but also causes many functional problems along the way. The Consortium for Information & Software Quality (CISQ) report indicates that poor-quality software costs about $2.08 trillion in the US alone.

It is crucial to build useful products and test them using a solid testing strategy for good test coverage. It helps benchmark the health of a product. Different test coverage techniques help in developing a testing strategy. In this guide, you’ll learn about the different test coverage techniques that every tester must know.

What does Test Coverage mean?

Test coverage defines what percentage of application code is tested and whether the test cases cover all the code. It is calculated as

For example, if you have 10,000 lines of code, your test cases should be able to test the entire codebase. If only 5,000 lines of code are tested out of 10,000, the coverage is 50%.

Test Coverage vs. Code Coverage

Code coverage is a metric related to unit testing. It measures the percentage of lines and execution paths in the code covered by at least one test case. It only measures how thoroughly the unit tests cover the existing code. Test coverage is a job for the QA developers and testers who measure how well an application is tested.

Benefits of Test Coverage

Before learning about the different types of testing coverage techniques, let’s look at the benefits of testing your application early and defining your test coverage.

• Early Detection: It helps to detect any errors in your application at the initial stages of software development. Identifying gaps in the requirements and test cases can save a lot of time and effort in the future.
• Eliminate Redundancy: It is unnecessary to consider all test cases sometimes. Developers can identify such redundant cases and report them to make the code lighter.
• Fewer Resources: Better test coverage means fewer defects in production and user acceptance testing defects. This translates to fewer resources allocated for testing.
• Smoother Testing Cycles: Test coverage helps optimize regression tests, test case prioritization, test suite augmentation, and test suite minimization. All these, in turn, help in a smoother and more efficient software development life cycle.

Test Coverage Techniques

Test coverage techniques help you track the quality of your tests and cover the areas that are not validated yet. Some popular techniques are

1. Product coverage which tells us how much of a product is covered
2. Risk coverage informs us about the risks in an application
3. Requirements coverage track how many of the requirements are met successfully
4. Compatibility coverage checks the compatibility across multiple browsers and devices
5. Boundary value coverage checks the tests around the minimum and maximum boundary values
6. Branch coverage checks the percentage of branches or decision points in the code that are executed

1. Product Coverage

Product coverage tells us which parts of a product are tested. Say there is a counter that is to be tested. A counter is a simple application that can either increment or decrement a number, similar to adding items to a shopping cart. The operations of the counter have to be tested i.e. incrementing and decrementing the counter. But there may be other factors that need to be tested. For example, should the counter handle negative numbers?

Product coverage can be increased by prioritizing requirements, preparing a checklist of testing requirements, and implementing effective test automation to reduce testing times. Several cloud-based test automation tools like BrowserStack allow users to set up their website for testing in a few simple steps.

A product with good product coverage verifies every possible scenario like the ones described above.

2. Risk Coverage

This test coverage technique helps to assess the risks related to the application and tests them thoroughly.

The above image gives us an estimate of what must be tested and how critical it is. It shows the probability of something happening and the (negative) business impact it would have. Based on this, four zones have been defined:

• Very likely scenario with high impact – It must be tested
• Unlikely scenario with high impact – It should be tested
• Very likely scenario with low impact – It could be tested if there is time
• Unlikely scenario with low impact – the test is too expensive for the value it provides, so testing is not required

Say there is an application that depends on a third-party API. There is a risk here of the API going offline. Analyzing how the application should work in such a case is what risk coverage is all about.

If you want to say that your application is covered, all of its relevant risks should be listed and answer the questions they elicit.

3. Requirements Coverage

Requirements coverage is the most basic and essential test coverage technique that helps assess if it meets the user’s requirements. It is simply a way of testing whether the required functionalities exist or not. If the software has promised certain deliveries, these promises must be met using this technique.

4. Compatibility Coverage

Device fragmentation is an exceptionally huge problem that many firms can run into because it can cause compatibility issues and hamper a product’s user experience. There are 9000+ devices, 8 browsers, and 21 operating systems available today. Testing across all combinations of device-browser-OS is a mammoth task. The compatibility test coverage technique ensures that the application is compatible across browsers and operating systems.

There are different categories of compatibility testing, such as:

• Browser Testing: Testing across browsers provides helpful information about how the application works across different browsers. BrowserStack Live provides 3000+ browsers and devices to test an application ensuring that you don’t miss out on your user’s preferred browser-device-OS combinations. Try for Free.
• Hardware Testing: The application is tested with different hardware configurations.
• Software compatibility: This involves testing the software with other software. An example would be testing Microsoft Word compatibility with Microsoft Outlook.
• Network testing: Assess the performance of an application in different network conditions like 3G,4G, and Wi-Fi.
• Mobile testing: It involves testing websites across different mobile devices and platforms like Android or iOS.

5. Boundary Value Coverage

Boundary Value Coverage is a testing technique that focuses on testing the boundaries and extreme values of input conditions. The idea behind this technique is that errors are more likely to occur at the edges of input ranges rather than within the normal range. By testing the boundary values, you can identify potential issues related to data handling, validation, and boundary conditions.

The Boundary Value Coverage technique involves selecting test cases that fall on or near the boundaries of input ranges. It typically includes four categories of values:

• Lower Boundaries: Test cases where inputs have the minimum valid value or just below it. This helps identify issues related to handling the lower limits and boundary conditions.
• Upper Boundaries: Test cases where inputs have the maximum valid value or just above it. This helps identify issues related to handling the upper limits and boundary conditions.
• Within Boundaries: Test cases where inputs fall within the valid range but are not at the extremes. This ensures that the system behaves correctly for typical inputs and helps verify the functionality and behavior within the normal range.
• Invalid Boundaries: Test cases where inputs are just outside the valid range or have invalid values. This helps identify how the system handles invalid inputs, such as error messages, validation checks, or graceful degradation.

The number of test cases required for boundary value coverage can vary based on factors like the complexity of the system, input ranges, and specific requirements. However, a common approach is to select test cases for the minimum valid value, just below the minimum, the maximum valid value, and just above the maximum for each input.

By applying Boundary Value Coverage in testing, you can increase the likelihood of detecting issues related to boundary conditions, constraints, and data handling, ultimately improving the quality and reliability of your software.

6. Branch Coverage

Branch coverage is a software testing metric that measures the percentage of branches or decision points in the code that have been executed during testing. A branch represents a point in the code where the program can take different paths based on a condition or a decision.

Branch coverage aims to ensure that all possible paths and outcomes within the code are tested. It helps identify areas of the code that have not been exercised, potentially indicating untested logic or potential bugs. The goal is to achieve high branch coverage to increase confidence in the reliability and correctness of the software.

To calculate branch coverage, the testing process needs to track which branches have been taken during execution. This can be achieved using techniques such as code instrumentation, where the code is modified to log information about executed branches, or using specialized testing tools that can track code coverage.

Branch coverage is typically reported as a percentage, representing the ratio of executed branches to the total number of branches in the code. For example, if a code section has 10 branches and during testing, 8 branches are executed, the branch coverage would be 80%.

Making the most out of Test Coverage Techniques

To build stable products, deciding on a test strategy is essential. A strong test strategy will help provide maximum test coverage for the code. The test strategy involves using the different test coverage techniques mentioned above. Although each technique has its own unique benefits, the QA team must decide and take the final call.

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With proper test planning, they can understand the features, risks, compatibility issues, and product requirements. Nowadays, test strategy techniques use AI with self-correcting test cases that learn from previous executions and improve upon them, significantly reducing test maintenance.

It is not easy to define a strong testing strategy for any application. But if done well, it greatly benefits the business and reduces the team efforts in the long run. They help track the progress and quality of your testing and help the business catch defects early on and decide which tests to perform and which to avoid. These test coverage techniques cover the various aspects involved in testing a product and help build an overall concrete testing strategy.