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Code Coverage: Assess and Ensure Confidence in Your Testing

Code coverage exposes the code in your application that has and has not been tested. Users can perform code coverage at various levels, function or unit, the entire file, or the entire application on target hardware or host environments. And you can aggregate the coverage from the various testing methods like unit testing and system testing.

What Is Code Coverage?

Structural code coverage is the identification of code that has been executed and logged for the purpose of determining if the system has been adequately tested.

Code coverage expresses the degree to which the application’s source code is exercised by all testing practices, including unit testing, manual testing, automated functional testing, and the like. It also:

  • Enables more accurate quality and coverage metrics.
  • Exposes dead code and untested or under tested parts of the application.

As a result, application coverage provides extremely powerful insight into risk. In most organizations, unit testing is the primary vehicle for driving coverage. And while unit testing is a valuable testing practice that also enables several process-oriented benefits, it is also expensive in terms of the expertise and time to create, manage, and maintain the tests.

Code coverage can be leveraged as part of the continuous integration (CI) process, as well as part of the developer desktop workflow. You can also perform advanced analytics on the source code and identify which unit tests need to be rerun based on code changes the developer has performed.

Plug-in electric vehicle with glow and motion blur and red light trails 3d rendering

These code coverage tools are especially useful in industries for embedded development of safety- and security-critical applications where software systems cannot fail, or lives will be lost.

The thoroughness of the coverage in safety-critical systems depends on the application safety integrity level (SIL or ASIL) metric used in various industries and the development assurance level (DAL) commonly used in avionics. Thoroughness refers to the structural elements in code. These are typically broken down to the code statement, branch, modified condition decisions and with Parasoft, you can also drill down to a much finer level of coverage granularity, such as the object code or assembly language.

How Is Code Coverage Measured?

Code coverage is often identified or measured through code instrumentation. This is done by adorning the source code with additional tracking code to determine while it runs whether each statement, branch, and/or modified condition decision (MC/CD) path has been executed.

What to Know About Code Bloat

It’s important to know that code instrumentation causes code bloat. The increase in code size isn’t usually a concern. For embedded targets with memory constraints, the increase may impact the ability to load the code onto your target hardware for testing.

Steps to Prevent Code Bloat for Embedded Targets

  1. Instrument part of the code.
  2. Perform the test.
  3. Collect the code coverage metrics.
  4. Repeat by instrumenting the other part of the code and un-instrumenting what you just tested.
  5. After testing all of the parts of code, merge the test coverage results for a full, measured view of code coverage for the entire application.

What Code Coverage Percent Is Ideal?

Code coverage percentage goals can be subjective in some cases. In other cases, they’re mandatory. When building applications that are safety-critical where failure may cause death, regulatory and industry standards require 100% structural code coverage.

For applications that aren’t safety-critical, code coverage tends to be left to the development organization to decide. The common comfort level for these types of circumstances is achieving a goal of 80% code coverage.

Top 6 Benefits of Code Coverage

Answers "Am I Done Testing?"

Code coverage can help measure test completeness and it guarantees that you have inspected every single line of code in your application through execution. Leveraging a combination of testing methods like static analysis, unit testing, system testing, performance testing, and the like, is the best way to ensure code quality.

Satisfy Code Coverage Compliance Needs

Fulfill code coverage requirements for functional safety standards like DO-178B/C, ISO 26262, ISO 21434, IEC 62304, IEC 61508, and EN 50128. Code coverage requirements help ensure code safety, security, and reliability by exposing untested code and flushing out defects.

Reduce the Cost Defects

Code defects found in production are the most expensive. Prevent them from slipping through the cracks by highlighting code that has not been tested before you release your application. This can be performed at the developer’s workstation or automated as part of the continuous integration (CI) pipeline.

Perform Assembly/Object Code Verification

For the absolute most stringent safety-critical code coverage requirements, such as DO-178C Level A, Parasoft offers code coverage at the assembly level. Save days — even weeks — of labor-intensive, error-prone manual effort with our automated solution.

Fulfill Code Coverage on Host and Target Hardware

Thorough testing of embedded safety and security-critical applications requires testing on-target hardware and in the host environment. Parasoft provides code instrumentation for both to capture and report structural code coverage for statement, branch, modified condition decision coverage (MC/DC), and more.

Attain 100% Code Coverage

Although you can generally achieve 100% structural code coverage goals through unit testing, save time and effort by aggregating your code coverage results automatically obtained from system testing. And then complete the remaining uncovered code using unit testing.

Structural Code Coverage Tools

Deploy Parasoft’s suite of products to conduct structural code coverage of applications written in C, C++, Java, C#, and VB.NET.

Parasoft C/C++test icon


Collect coverage from unit testing, system testing, manual testing, as well as all other test execution methods used. Parasoft C/C++test supports a range of coverage metrics (Branch, Statement, MC/DC, etc.), which teams can use in native and cross application development.

Parasoft Jtest icon


Collect and monitor code coverage during manual or automated functional testing performed on your Java application. Users can send coverage data and test results to merge and correlate for analysis, which provides insights about how well the application is tested and your test quality.

Parasoft dotTEST icon


Collect code coverage information for standalone and web applications written in C# and VB.NET. Install the monitored application on the same machine where dotTEST is installed or on another machine.

8 Best Practices for Code Coverage

Obtaining the amount of code exercised during testing is a powerful metric in order to understand the level of risk remaining in the application. Here are some best practices to follow.

CI Pipeline

Integrating testing and code coverage into your build system will increase efficiency, promote collaboration, and provide greater visibility across your entire software development lifecycle.

System Tests

Take advantage of your system tests to obtain code coverage and identify missing tests that may exposed hidden bugs.

Coverage Advisor

Don’t burn time trying to determine all the input values and preconditions required in a test case in order to get coverage on an elusive statement, branch or MC/CD line of code. Use coverage advisor.

Aggregate Coverage

Use the various testing methods that you have to perform to expedite your coverage requirements. Aggregate coverage can be obtained from system, integration, unit, and manual testing.

Automated Test Case Generation

Parasoft solutions can automatically analyze and generate unit test cases to flush out null pointer issues, out of boundary value conditions, divide by zero, and many other types of defects. In addition, these test cases can be enabled to produce code coverage and, in some cases, get you up to 90% structural code coverage.

Partial Instrumentation

Code instrumentation causes code bloat and the increase in code size may impact the ability to load the code onto your memory-constrained target hardware for testing. Instrument portions of your code at a time, run your tests, and aggregate your coverage metrics from each run.

Debugger for Coverage

If you have to satisfy 100% structural code coverage but have defensive code that will only execute upon the system entering into a fault state that could take weeks, months, or even years (or perhaps never), use your debugger to simulate the conditions needed and perform a visual inspection of the code execution/coverage.

Dead Code

If code is found because it has no pathway to its execution, for security and safety concerns, make sure it is deleted and never gets out into the field.

How to Get Started With Code Coverage

Screen capture of Parasoft Report Center Complete Code Coverage dashboard.

Parasoft code coverage within the IDE and DTP dashboard reporting and analytics solutions.

1. Become Familiar With Your Coverage Requirement Needs

To get started in collecting code coverage, become familiar with your coverage requirement needs. Maybe your industry and type of application don’t require any coverage metrics to be obtained, but you want to ensure or improve code quality, so 75% might be your initial goal.

If your industry requires compliance to a functional standard like DO-178C for avionics or ISO 26262 and ISO 21434 for automotive or IEC 62304 for medical, then determine if you need to obtain 100% code coverage or another percentage of code coverage is recommended. Also, know what structural code coverage type you need to satisfy. It could be the function, line, statement, block, call, path, decision, simple condition, MC/DC, object/assembly, or a combination of these.

2. Obtaining Code Coverage

One of the easiest ways to obtain code coverage is during implementation when engineers are creating unit test cases to test their code. With solutions like Parasoft C/C++test, C/C++test CT and Jtest,

  • Users get a very short learning curve since it integrates right into your IDE and provides this functionality.
  • QA teams can reuse these unit test cases for regression testing and/or as part of the build process in an automated CI pipeline workflow.

Be aware that instrumenting the code can cause code bloat and if you are testing on target hardware you may need to do partial instrumentation. Instrumented code may also alter the performance of the execution, so you may want to become acquainted with various optimization features available to you.

3. Collecting and Reporting Your Code Coverage Metrics

Collecting and reporting your code coverage metrics is crucial. There are several methods based on if your application is running on an embedded target, or a fully resourced system or server.

Ultimately, you’ll obtain or merge coverage data to get your full code coverage metrics. Coverage reports can be generated from your IDE, and they can be exported to Parasoft’s reporting and analytics dashboard DTP. In DTP, users can visually inspect the high-risk areas, understand what should be addressed next, and produce compliance and audit reports.

Why Parasoft Code Coverage Tools?

Parasoft’s solution for code coverage provides critical feedback about the completeness and thoroughness of the testing process, by correlating tests and structural code coverage results. You can use these results or metrics for assessing unit, integration, and system-level testing completeness through our support of all important types of code coverage (function, call, line, statement, block, path, decision, simple condition, and MC/DC), including object/assembly coverage.

Coverage results are available directly in the IDE, with convenient views and highlights in the source code editor, as well as in the form of static HTML or pdf reports, and dynamic reports through Parasoft’s centralized reporting dashboard.

Users can monitor applications executed natively on the desktop, cross-platform using simulators, or on real embedded hardware. C/C++test and C/C++test CT’s coverage module is optimized to minimize the impact on the execution performance and test binary footprint, which makes it suitable for use with high-end, server-based applications, as well as very limited systems based on 16-bit microcontrollers.

When connected with Parasoft’s Process Intelligence Engine, users benefit from test impact analysis. For each and every test performed, including manual, system-level, or UI-based, tests are recorded for not just test/fail and results but also their coverage impact on the codebase.

Each additional test is overlaid on this existing information, creating a complete picture of test success and coverage. As code is changed, the impact is clearly visible on the underlying record, highlighting coverage tests that now fail or code that is now untested. Raising this information in various degrees of detail allows developers and testers to quickly identify what needs to be altered/fixed for the next test run.

With Parasoft, teams can concentrate on code coverage for the areas of active development, instead of the entire codebase, which can be especially problematic when working with legacy codebases. Rather than solely trying to achieve a coverage number for the entire codebase, Parasoft helps you pinpoint the parts of the code that are changing.

Parasoft’s reporting dashboard correlates the data from C/C++test or C/C++test CT with observed changes in the codebase to focus the development team on achieving higher levels of code coverage for those specific, modified parts of the codebase. With Parasoft, you can minimize the impact of changes by efficiently managing the change itself.

Frequently Asked Questions