Detailed Guide On Test Coverage: With Best Practices

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  • Detailed Guide On Test Coverage: With Best Practices


Test coverage is a black-box testing method that entails testing elements included in the functional requirements specification, software requirements specification, and other required documents. Since the tests are derived from these documents, there is minimal or no chance of automation.

For example, say you want to perform cross browser testing on your web application to see if it renders properly in different browsers and operating systems. Your test coverage would be about equal to the number of browser + OS combinations for which you have tested your web application's browser compatibility.


What is Test Coverage?

Test coverage is a crucial software testing metric that determines the code covered during the test runs. In other words, it is used for evaluating the test execution coverage in the software application.

It is a type of black box testing methodology where test cases are written in a manner that provides maximum coverage of requirements stated in the requirement specification document. Since the tests are derived from these documents, there is minimal or no chance of automation.

Test coverage involves validating the features implemented as a part of your requirements documentation, such as the functional requirements specification and software requirements specification.

If you have to perform cross browser testing to ensure that your web application renders well from different browsers, you would be covering many browsers and operating systems.

To calculate test coverage, you can divide the number of lines covered by a test by the total number of lines in your application’s test code.

Test coverage = line of code covered by test*100/total lines of code

Besides, we have code coverage as well. These two terminologies are sometimes confusing for both testing teams and development teams. Test and code coverage are two of the most popular methodologies for evaluating code effectiveness. These terms are sometimes used interchangeably due to their similar underlying principles. However, they are different from what you might think. To know more about how test and code coverage differs from each other, read our article on code coverage vs. test coverage.or can also read What is code coverage?


What is the purpose of Test Coverage?

Test coverage acts as an indirect quality check method as it helps identify a quantitative measure of how much code you cover. A secondary purpose of it is the creation of additional test cases that further helps in increasing coverage.

Additionally, it helps identify gaps in test cases and requirements. Therefore, testers can spot defects early in the software testing life cycle (STLC). It eliminates a lot of grunt work that testers would have had to do at a later stage. Indirectly, this leads to a fine end product, further enhancing customer satisfaction.

Test coverage helps in removing test cases of low to no relevance to the current project. In other words, when a developer reports an unnecessary test case, the overall code becomes lighter. On the other hand, it also helps discover some portions of software that a test case might not have covered. As a result, your program becomes error-free and more robust. With extensive data available on different coverage items, coverage access increases with better testing effectiveness.

Benefits of Test Coverage

In this section, we will cover some striking benefits of test coverage and why every tester should care about it. Otherwise, why bother learning the metrics, techniques, and steps to enhance it if you don't even know how beneficial it is?

  • Kills the bug: It helps terminate the bugs & defects of the code in its early stages. This way, the testers don’t need to spend their time and resources hunting for the bugs right before the product delivery when the complexity of the code has risen. A direct impact of this course of action is the reduction in the utility of resources increases the ROI and, in turn, the net profits.
  • Eradicates redundancy: Redundancy can be annoying and savage on time & money simultaneously. It can worsen the complexity of code and hinder its overall framework. Test coverage helps developers identify redundant cases and report them to make their code lighter.
  • Expands testing scope: When you focus on something, it improves. Similarly, implementing test coverage on the software product widens the testing range. And successively, with a broader scope, the efficiency of testing increases, with better traceability and identification of defects in the test cases.
  • Improve quality: With a higher likelihood of detection of bugs & defects, test coverage provides indirect quality assurance. It also appends extra test cases. These cases ultimately lead to improvement in quality. On top of that, it acts as a reliable source of information for clients and stakeholders.
  • Streamline testing cycle: The software development life cycle is a tricky process. Test coverage helps unravel the complexity of this process while determining ways to fix defect and regression test leakages effortlessly.

Types of Test Coverage

For test coverage, there are four primary techniques.

This classification is based on the facets of the application prioritized in the coverage.

  • Product coverage: This technique revolves around the user's perspective. It involves test cases that examine every possible entry-exit outcome of the product. In simpler words, product coverage deals with the if-then-else statement chart and related conditions.

    In turn, this process leads to the determination of the scope of the application. Practices like checklists, priority charts, automation, etc., can extend the range of practice coverage.

  • Risk coverage: It incorporates the analysis of all the inherent risks in the product. Measures like risk enlistment, likelihood, and threat are covered through this technique. This can be the most critical coverage technique for applications more prone to impactful risks. Risk coverage assures the stakeholders about the proper risk & regression management.
  • Requirement coverage: The requirement coverage technique focuses on the application product's essential aspect— meeting the requirements. No matter how well built, examined, and secured the product is, it’s just fool’s gold if it doesn’t meet the functional needs it is built for. This is arguably the broadest coverage technique as it ensures the demand fulfillment facet of each component and, thus, comprises a plethora of test cases.

    Requirement coverage is implemented from a combination of the user's and developer’s perspectives. It is the fundamental process for every software product, regardless of its genre, complexity, or approach. This technique also involves the coverage metrics like implementation rate, case-requirement analysis, etc.

  • Compatibility coverage: This class of coverage techniques measures the application's compatibility range across different platforms, browsers, and operating systems.

    It involves test cases that meet the requirements for testing the product’s cross-platform performance. However, with such a broad spectrum of platforms, you must avoid redundancy in the testing pattern. The test coverage may only include the prominent and more usable platforms depending on the availability of time and resources.

    To test your compatibility coverage, one can use cloud-based cross browser testing platforms like LambdaTest to their websites and mobile apps on an online browser farm and device farm of 3000+ real browsers, devices, and OS combinations. With its real device cloud, you can test use cases in real-world environments and get accurate results.

    Subscribe to the LambdaTest YouTube channel for software testing tutorials around Selenium testing, Playwright browser testing, Appium automation, and more.

  • AI automation coverage: Going by its name, this coverage technique relies entirely on AI automation instead of manual enlistment, arrangement, etc. Considering the recent development of Artificial Intelligence at the functional level, this is a high but reasonably cost coverage technique.

    However, the outcome of utilizing AI-aided automation tools is visible in the performance and output. The process becomes incredibly effortless yet high-quality. Powered by AI, the test coverage keeps improving for the entirety of its life.

Test coverage techniques are undoubtedly intricate. And so is the information they comprehend. Thus, testers need to understand and implement them very cautiously.

Test Coverage Metrics

For a document comprising assessable data, nothing is more important than metrics (along with its presentation). Test coverage metrics are the hub of all numeric information and formulae relevant to the application code and the testing process.

Based on the grounds of functionality, metrics can be classified into three major categories: Code testing, data testing, and application testing metrics.

  • Code testing metrics: The test implementation rate is one of the simplest code-level metrics. This is a piece of crucial information concerning the progress of testing.

    The basic formula for the test implementation rate is,

    ‘Number of tests executed*100/Number of tests planned to be executed’.

    The metric is easy to present but needs more critical information about the project's quality and complexity.

  • Data testing metrics: This class of coverage metrics involves dynamic information that relates testing conditions with the application's components. With changes in test cases and components, you can utilize this castable data for the effect that the change brings. It encompasses metrics like requirement attainment rate, case-requirement table, etc.

    The requirement coverage rate also has a basic formula,

    'Number of requirements attained*100/Total number of reqirements’.

    On the other hand, case-coverage analysis is a tabular statistic that exhibits testing conditions of respective features along with the result of testing. It is arguably the most crucial statistic, especially from the approvers’ point of view.

  • Application testing metrics: The most holistic aspect of coverage metrics is the data relevant at the application level. This category of statistics is more rigid and of little use when dealing with test cases. Details like defect density, unfinished coverage study, etc., are a part of application testing metrics.

    Defect density, with a simple formula— number of defects detected/size of the application is a dynamic yet essential piece of information. Not only does it help realize the requirement of retesting, but it also gives an idea about the necessity of automation in different test cases. It is the most dependable source of information to base the position of defect elimination/testing on the priority list.

    The unfinished coverage study is the direct counterpart of the case-requirement study. It contains the test cases yet to be matched with the instructed requirements and the current status of the process. Some other similar metrics that may be relevant to the testing approach and project requirements are defects for requirement, testing per defect, etc.


How to enhance Test Coverage?

The difference between average and impressive coverage is small but crucial. To upgrade the level of coverage, testers need to sincerely keep a few practices in mind.

Following are the practices that will ensure better quality coverage for every individual claiming involvement in the product’s development & delivery:

  • Assemble Information: Documentation of literally any comprehensive data asks for research. It is essential to thoroughly research the product, testing requirements, and every other factor that takes part in its development.

    Testers, engineers, and developers must have information like the market share of the product, competitors, general trends & data of the users, etc. It is equally important to document this data systematically. You can use visual data representation methods like tables, pie charts, and venn diagrams.

  • Assess Compatibility: After gathering complete information about the product, testers should analyze the compatibility aspect of the project. For enhanced coverage, it is essential to assign specific testing devices for particular platform compatibility testing in the correct category.

    These categories can include:

    • Devices commonly used by relevant customers.
    • Popular devices developed long ago. They give an idea about compatibility in bygone processing conditions.
    • Devices with early access to platforms and OS. They allow proper testing time for engineers before the operating system becomes relevant.
    • Devices gaining consistent attraction in the market and emerging to attain the commercially prior category.
  • Arrange Environment: Attaining the apt testing environment is very crucial. An essential measure in the testing process is the imitation of consumer-friendly ambiance. Components like domestic WiFi connectivity, CPUs, drivers, RAM/ROM, etc., must be duly incorporated into the testing environment.

    Even the subtlest factors, for instance, the application’s performance in portrait and landscape mode, must be scrutinized. According to a few experts, testing in natural user ambiance is the game-changing factor in coverage enhancement.

  • Analyze combinations: Now that the research, compatibility, and environment are sorted, it is time to execute the test cases on various devices. To ensure higher productivity, it is essential to select the right combination. You must choose a few devices from every class categorized on priority, performance, and compatibility.

How to expand Test Coverage in a shorter interval?

Efficiency is the key. The only thing better than completing a task is doing it quickly. Here are some factors that can help expand the coverage of your tests in a short interval:

  • Maintain checklists: Checklists are handy and practical. Maintaining a checklist can help in keeping track of progress.
  • Prioritize carefully: Prioritizing test cases significantly saves time and resources. Testers should categorize test components and risks into the major, minor, and rejectable.
  • Simplify data: The data processed from the research must be short and meaningful. Use logical or visual descriptions during documentation.
  • Analyze initial impacts: Examining the defects and bugs in the early stages is a vital aspect of coverage. This method saves time & redundancy while also preventing dealing with the code in its complex final stages.
  • Integrate prioritization with compatibility: Perform cross-platform testing only on test cases higher on the priority chart while approving the fewer prior ones through a single browser, OS, etc.

How to use Automation to increase Test Coverage?

To systematically incorporate automation into the test coverage to improve its quality and accuracy, testers need to pre-define a specific procedure. Following is a detailed description to get an idea of the procedure.

  • Identify the testing components with automation requirements: To do this, analyze their positioning on the priority list, risk likelihood, and importance in the application code.
  • Choose the relevant testing tool: Examine the suitability, features, flexibility, and, most importantly, the cost of the test tool.
  • Employ experienced or skillful individuals to script the tool: Ensure their understanding of the product and the tool.
  • Construct systematic and high-quality data: To ensure better performance of the test execution tool, ensure that the data and the data source are compatible and readable by the AI. If possible, utilize data generator software.
  • Stability of test tool: If the application is likely to change/update, ensure that the test tool remains unaffected.

Furthermore, it’s always wise to run automated tests on automation testing platforms like LambdaTest to cut your in-house testing costs. LambdaTest provides a cloud-based scalable test infrastructure that will exponentially increase your browser coverage by running your test scripts on a cloud of 3000+ desktop and mobile environments.

Test Coverage Best Practices

Testers must follow some commonly recommended practices to achieve the quality threshold. These may differ with differences in the application genre, priorities, requirements, etc. However, understanding the basic idea will likely affect the coverage positively. Some healthy practices include:

  • Keep updates in mind: A factor that often slips from testers' minds is that the coverage must have a scope that incorporates the updates/changes the product will undergo. The advisable coverage limit to effortlessly acknowledge changes is 90%.
  • Quality is better than quantity: Quality has always had the edge over quantity. Even from the stakeholders' perspective, the prime concern is eradicating bugs, defects, and regression from high-priority & risk-prone components. Executing a well-thought test coverage on a few high-priority test components is preferable to having a broad and hazy scope of the coverage.
  • Say no to redundancy: Useless data duplication is more damaging than it seems. Not only does it squander resources, but it also decreases the overall quality of the coverage directly or indirectly. Moreover, the duplication of test suites makes it rather strenuous to identify and eliminate defects from the code.
  • Perform multi-degree testing: Implementing test cases at every level of the code is crucial. The three testing levels are:
    • Unit testing- Executed on the smallest testable unit of the code. This elaborate testing pattern ensures the absence of bugs and defects in every code component.
    • Integration testing- Examines smooth networking between the different modules inspected in unit testing.
    • System testing- The final testing level executes the approach to the overall software product. In simpler words, it is an end-to-end testing pattern that ensures that the final product runs smoothly, even in the user environment.
  • Automation is essential: Even for its high cost, automation, to whichever extent it is affordable, is critical. AI automation is a must-have, especially for high-priority test cases that demand accuracy.


Now that we understand the role test coverage plays in measuring and ensuring quality software, it's time for implementation. We hope that this comprehensive guide and the best practices inspire businesses to put these to good use.

Frequently Asked Questions (FAQs)

How do we measure test coverage?

To calculate coverage of your tests, divide the total number of lines in a software application by the number of lines covered by each test.

What is good test coverage?

According to the consensus, 80% coverage is a good target. Reaching a higher coverage level might be expensive while not producing enough benefits.

What is test coverage in software testing?

Test coverage in software testing refers to the extent to which a software application or system has been tested. It measures the percentage of code or functionalities covered by test cases, ensuring that all critical aspects of the software are tested.

How to measure test coverage?

Test coverage can be measured by using code coverage tools that track which parts of the code are executed during testing. These tools generate reports showing the percentage of code covered, helping identify areas that require additional testing and improving overall testing effectiveness.

How to improve test coverage?

To improve test coverage: 1. Identify and prioritize test scenarios based on the requirements analysis, 2. Use a combination of testing techniques and tools, 3. Perform risk-based and exploratory testing, 4. Enhance test cases based on feedback and lessons learned, 5. Leverage test automation for efficient and extensive testing, 6. Collaborate with stakeholders and track test coverage metrics.

What is test coverage in manual testing?

Test coverage in manual testing means how much of the application's functionality and code is covered by the tests performed manually. It helps determine how well the manual testing process ensures that all important parts of the application are tested and working correctly.

How much test coverage is enough?

The optimal level of test coverage depends on various factors such as project complexity, risk tolerance, and resources. There is no fixed percentage, but aiming for a range of 70-80% coverage is generally considered good practice.

What is maximum test coverage?

Maximum test coverage refers to achieving the highest possible level of test execution to ensure thorough testing of requirements and functionalities outlined in various documents such as FRS, SRS, and URS.

How can I improve my test coverage?

To improve test coverage, create comprehensive test cases that cover a wide range of test scenarios relevant to the current release. Prioritize testing before the release to efficiently cover more scenarios within a scheduled timeframe.

What is 100% test coverage?

Achieving 100% test coverage means ensuring that all parts of your code are tested by unit tests. It helps identify and fix bugs before they impact users, improving code quality and reducing the risk of undetected issues in untested portions of the codebase.

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