The document explores the differences between code coverage and test coverage, emphasizing that code coverage is a white-box testing technique assessing executed code, while test coverage is a black-box technique evaluating test execution against requirements. It outlines best practices, advantages, and disadvantages of each method, detailing how they can be complemented for effective software quality assurance. Moreover, it provides insights into various coverage types and emphasizes the importance of a comprehensive testing strategy to mitigate defects and improve application reliability.

1. Code Coverage vs Test Coverage: A
Complete Guide
Test coverage and code coverage are essential tools to analyze the software
and measure the effectiveness of its codebase in development. They could be
interchangeable, but they are different. This article explains what makes them
different to help your understanding.
What is Code Coverage?
Code coverage is a white-box testing technique. It verifies the extent to which
developers have executed the code. The tools used for code coverage contain
static instrumentation. Testers can use these to insert statement monitoring
code execution at crucial points in the code.

2. While adding instrumentation does increase the test execution time and code
length, the information received by the tester due to this more than justifies
the increase. Testers receive a report from the code coverage scripts detailing
the extent to which the developers have executed the application. Testers will
analyze the result to understand the product, make their tests effective, and
reduce possible defects after release.
Why perform Code Coverage?
Developers perform code coverage at the unit test level; this gives them a
great vantage point to help them decide the tests they need to include. Code
coverage helps them answer questions like:
● Does the unit test suite have enough tests?
● Has the code been implemented intentionally?
Further, as development progresses, developers add new features and fixes to
the codebase, changing the code to stay updated with these changes while
trying to maintain the established testing standards. Code coverage ensures
developers maintain these standards, and only optimal quality code remains.
A higher code coverage percentage means lesser chances of overlooking
unidentified bugs. It helps when you set up a minimum level that code
coverage must achieve to reduce the chances of finding bugs at later stages
of the development process.
Code Coverage Best Practices

3. 1. Aim for Balanced Coverage Goals: Avoid setting an arbitrary 100%
coverage goal, as it can lead to unnecessary tests that may not add
value. Instead, aim for practical, high-impact coverage percentages
that ensure critical areas are covered.
2. Measure Relevant Metrics: Depending on your application
requirements, focus on different coverage types, such as statement,
branch, and path coverage, to ensure that all code paths have been
adequately tested.
3. Identify Gaps Early: Use code coverage tools to identify areas with low
coverage during development. This will help address them proactively
and reduce the risk of issues.
4. Encourage Developer Ownership: Encourage developers to write unit
tests for their code and track coverage as part of the development
process. This increases accountability and builds a robust codebase
from the start.
5. Continuously Integrate Coverage Checks: Integrate code coverage
tools into the CI/CD pipeline to consistently monitor and enforce
coverage standards with each code change.
Benefits of Measuring Code Coverage
● A high percentage of software is less likely to contain defects
resulting from non-adherence to coding practices, overly complex
code, or coding errors.
● A high percentage can imply that the code is more readable and
maintainable.

4. ● It helps provide stakeholders not involved in the software
development process with a way to gauge software quality.
● Since a larger team leads to ambiguity when defining well-tested
code, this process acts as an approximation metric, unifying the
team's understanding of a well-tested code and leading to a more
consistent test practice.
Levels of Code Coverage
Method Coverage (Function Coverage)
Testers measure code through method or function coverage by counting the
number of functions a test suite calls.
Statement Coverage
Statements are instructions highlighting an action a program needs to carry
out. Statement coverage hence measures the percentage of code statements
and gives an accurate estimate of the quantity of code the tests execute.
Branch Coverage
Branch coverage measures whether a test suite executes the branches from
decision points written into the code. Such decision points arise from if and
case statements, with two possible outcomes: true and false.

5. Testers use branch coverage to verify if their test suite executes the branches
from decision points in the code. These are typically statements with two
possible outcomes: a true and false or an if and case statement.
The goal is to verify if the tests execute all branch points across a
comprehensive set of inputs. It helps testers measure code logic.
Condition Coverage
Developers use condition coverage to verify if tests execute statements using
boolean expressions in the code - this is another way of ensuring that tests
perform all possible code paths.
Multiple Condition Decision Coverage (MC/DC)
Each decision statement can have a combination of conditions. Multiple
condition decision coverage ensures that tests execute all these
combinations seamlessly. Testers use this metric to test safety-critical apps
like those inside aircraft.
Parameter Value Coverage
As the name suggests, parameter coverage ensures that tests cover all
possible parameter values for each program. This metric is essential as
neglecting specific parameter values leads to software defects.
Cyclomatic Complexity

6. Testers use the cyclomatic complexity metric to measure the number of
linearly dependent paths in a program's source code. It is also helpful to
determine coverage for particular code modules.
Code Coverage Advantages
● You can use it to determine the quality and performance of any
software.
● Code coverage helps maintain the code base.
● You can evaluate the quantitative measure of code coverage.
● It helps analyze the software verification process and access the test
suite's quality.
● It exposes harmful and unused code.
● You can use it to create additional test cases.
● It increases time to market by increasing efficiency and productivity.
● It helps identify uncovered test cases.
● You can use it to measure test implementation efficiency.
Code Coverage Disadvantages
● It cannot always cover code entirely and accurately.
● You cannot test all feature values; it does not come with this
guarantee.
What is Test Coverage?

7. Test coverage is a black-box testing technique that provides details on tests
executed on an app or website. Testers use it to ensure maximum coverage
(according to the requirements outlined in documents like FRS (Functional
Requirements Specification), URS (User Requirement Specification), and SRS
(Software Requirements Specification), and to monitor executed tests.
How To Perform Test Coverage?
You can perform test coverage through various tests. However, the type of
tests you run depends on your testing team's business priorities. For example,
an organization building a user-centric web app will prioritize UI/UX tests over
functional testing.
Here are some test coverage mechanisms, the scope could depend on
definitions:
Functional Testing:
Functional testing involves testing app functionalities against client
requirements or those mentioned in the FRS documents.
Unit Testing:
Testers perform unit tests at the unit or module level. Bugs found at this level
differ from those found at the integration level.
Integration Testing:

8. Integration testing is also called system testing. Testers perform this test
once developers integrate all software modules.
Acceptance Testing:
You use this test to determine if a product qualifies for customer use.
Typically, developers must receive approval from SMEs and testers to push
code changes from staging to production.
Testers use test coverage depending on the level at which they perform the
tests and the type of software they're testing. Moreover, test coverage metrics
are different for mobiles and websites.
There are many times of test coverage and you can measure them at various
testing levels like component testing, integration testing, or acceptance
testing.
Here are some coverage types:
Features Coverage
Features coverage involves writing test cases to help implement maximum
coverage of product features. These test cases must test all mandatory and
optional features according to the priorities set by the product team.
Risk Coverage
Risk coverage addresses the risks associated with the project. It helps
mitigate these risks by identifying the core issues. However, we cannot predict

9. risks due to changes in market conditions. Hence, we cannot use risk
coverage at this stage.
Requirements Coverage
Requirements coverage ensures that when you write test cases, they provide
maximum coverage according to set requirements. Such a requirement can be
the default language for an SMS application - which is usually dependent on
the location of where the app is released.
Types of Test Coverage
Test coverage evaluates how thoroughly the testing process examines the
application's code and functionalities. Key types include:
● Statement Coverage: Measures the percent of executable statements
in the code executed during testing. It ensures that each line of the
source code has been tested at least once.
● Branch Coverage: Ensures every branch in the control-flow graph has
been executed. For example, given an if statement, the true and false
branches are tested.
● Condition Coverage: Verifies that each Boolean sub-expression has
evaluated to be both true and false. This ensures that all possible
outcomes of each condition are tested.
● Path Coverage: Has every possible route through a given code been
executed? This ensures that all potential execution paths are tested.

10. ● Function Coverage: Checks whether each function or subroutine in
the program has been called during testing.
Employing a combination of these coverage types helps identify untested
parts of the code, thereby enhancing the software's overall quality and
reliability.
Code Coverage vs. Test Coverage: How
to Choose?
While both code coverage and test coverage aim to improve software quality,
they have a different focus:
● Code Coverage: Measures the code executed during testing,
providing a quantitative assessment of test thoroughness. It helps
identify untested parts of the codebase.
● Test Coverage: Assesses how well the testing validates that the
application meets its requirements and provides the desired user
experience. It focuses on ensuring that all functionalities are tested.
Choosing between them depends on your project's specific needs:
● Opt for code coverage to ensure that all parts of the code are
executed, which is crucial for identifying dead code and untested
paths.

11. ● Opt for test coverage when focusing on validating that all user
requirements and scenarios are thoroughly tested, ensuring the
application behaves as expected.
In practice, combining both approaches provides a more comprehensive
testing strategy, balancing the depth of code execution with the breadth of
functionality validation.
Disadvantages of Test Coverage
While test coverage is a valuable metric, it has its limitations:
● False Sense of Security: High test coverage percentages can be
misleading, as they don't guarantee the detection of all defects. Tests
might execute code without verifying correct behavior, leading to
undetected issues.
● Quality of Tests: Test coverage measures the extent of testing but
not the quality. Poorly designed tests can achieve high coverage
without effectively validating the application.
● Resource Intensive: High test coverage can be time-consuming and
may divert resources from other critical testing activities, such as
exploratory or usability testing.
● Maintenance Overhead: Extensive test suites require ongoing
maintenance, especially as the application evolves, to ensure they
remain relevant and effective.

12. Recognizing these disadvantages is crucial for developing a balanced testing
strategy that maximizes test coverage's benefits while mitigating its
drawbacks.
Test Coverage Best Practices
1. Define Clear Objectives: Locate what you aim to achieve with your
tests, whether it’s ensuring functionality, reliability, or performance. Set
priorities based on critical application areas.
2. Focus on High-Risk Areas: Concentrate testing efforts on modules
that are prone to defects or have been frequently modified. Critical
functionalities and components that directly impact user experience
should receive higher coverage.
3. Optimize Test Cases: Avoid redundant tests and ensure each test case
adds unique value. Remove or update outdated test cases to keep the
suite lean and relevant.
4. Regularly Review Coverage Metrics: Monitor and evaluate test
coverage metrics to align with project changes. Adjust coverage goals
based on new feature additions, changes, or refactoring.
5. Integrate Automation: Use automated testing tools to cover routine
and repetitive tasks, enabling faster feedback and maintaining high
coverage with minimal manual intervention.
Why Is Test Coverage Analysis
Important?

13. Test coverage analysis ensures the identification of defects that you can
address. Here’s why it is essential:
Users Don't Tolerate Bugs.
A report from Statista highlighted that in 2019, 25% of users stopped using a
mobile app after just one use. Users will abandon an app that is glitchy or has
many unexpected behaviors.
Running Various Tests Is Important
To ensure your app or website meets all requirements stated in the agile
testing manifesto, you must cover all testing types in your development
process. You'll need to run performance, security, functional, accessibility, and
other tests to prevent defects. To ensure app responsiveness and quality,
you'll need to perform tests under real user conditions.
Developing and Implementing a Comprehensive Test
Coverage Strategy
To ensure your test coverage strategy is effective, you need to ensure
accuracy in:
● How you build and maintain your test labs.
● The platforms you include and use to test.
● Testing scenarios you build and execute for each software iteration.
HeadSpin: A Part of Your Test Coverage Tools

14. The HeadSpin Platform is a great test coverage tool that you can use to meet
your test coverage requirements. Its Create Your Own Lab (CYOL) product lets
you organize and utilize your existing device investment by delivering
uninterrupted local access to remote devices. You can use this to test and
debug critical workflows remotely. With CYOL, you get 68% fewer hours on QA
and 30% faster in-app load time.
The HeadSpin Platform supports all kinds of testing. It supports 30+
automation frameworks, lets you perform tests in real user conditions and
execute tests in parallel, contains real SIM-enabled devices, and provides
cross-device and cross-browser support.
Advantages of Test Coverage
● It reports on portions of the codebase that necessary test cases have
not covered.
● It helps detect areas of test cases that don't apply to a project. You
can eliminate these cases to make the code light.
● Developers can use it to create additional test cases when required to
ensure maximum test coverage.
● You can use it to prevent defect leakage.
Conclusion
Code coverage is an essential metric; however, test coverage is what you
should aim to achieve. By going beyond unit tests to acceptance tests,

15. integration tests, and others, you ensure your app is without glitches and is
ready for production.
However, even with test coverage, ensure you develop a strategy as testing
often without one does not always result in good. Understanding your
requirements and then testing is the best approach you can take.
This article was originally published on:
https://www.headspin.io/blog/a-detailed-guide-to-code-coverage-and-test-cover
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