Testing your code is a fundamental part of the modern software development process. It’s important to write tests and run checks each time you add new features or make changes to your app to ensure stability and reliability.
But what if you want to see how much of your source code is tested? For instance, you could have an application with multiple cases, and you may want to verify that your tests are covering each one of them. Enter code coverage.
Code coverage tools use multiple criteria to measure the percentage of code that was executed while running your automated tests. Usually, these measuring criteria include:
- Line coverage: the percentage of lines that have been executed in your source code
- Function coverage: how many of the functions you defined have been called
- Statement coverage: the percentage of statements executed by your tests
- Branches coverage: how many branches in your app (if statements, loops) are covered by tests
- Condition coverage: how many and, or, and xor expressions have been tested for all possible combinations of true and false
This article explores several specific scenarios that explain what code coverage is and how it can be helpful to your team.
Why Do You Need Code Coverage?
Code coverage is not just another vanity metric for your project, but a way to identify which code is and is not tested. When done right, it provides you with the data you need to have greater confidence in your tests. While a high percentage of code coverage doesn’t guarantee a bug-free application, it does give you confidence by identifying which code has been tested and which parts of your product may be vulnerable to errors.
Tracking code coverage can also help improve your overall developer workflow. As an example, tools like Codecov allow you to set automated checks to fail a code change if you don’t reach a certain percentage goal. This motivates your team to write missing tests.
When Should Your Team Adopt Code Coverage?
Apart from these advantages, there are many other specific scenarios where code coverage can become the secret ingredient to enhancing your project’s quality. Let’s take a look at a few instances in which code coverage becomes a particularly useful tool.
When Your Team Is Working in a Highly Regulated Industry
Sometimes, code coverage is not an optional addition to your product but a legal obligation. For instance, the automotive industry has a standard called ISO 26262, which defines all the requirements that electronic systems on a car must pass in terms of testing and security, eg, interface testing and fault injection testing. Other strictly regulated industries defining coverage requirements include the aerospace and medical sector, and the energy industry.
In all these cases, incorrect code can mean the difference between life and death. Code coverage is adopted to mitigate these circumstances as much as possible.
When Your Team Is Testing a Legacy Codebase
While any codebase can lack tests or have some tests spread across the app without any particular system, this problem is especially stark for legacy codebases. They tend to have outdated documentation and have badly maintained testing suites with old sections no developer dares to touch in fear of breaking the whole app.
When approaching a legacy codebase, having code coverage in place can be a great way to measure your progress in refactoring an old project. A code coverage tool lets you establish the percentage of code covered by pre-existing tests.
Once you’ve identified which parts of the product you want to focus on first, you can start writing tests for those areas. For example, if you want to make a critical service in your system more reliable, you can write multiple tests for it and assess its functionality. With time and consistent effort, your percentage coverage will grow, helping you to track your team’s progress and guide you during the refactoring process.
When You Want to Reduce Production Bugs
Naturally, a faulty product will not last long in the modern software market. If you’ve realized that your production code has bugs, code coverage can help you get things back on track.
While this metric is not a measure of the number of bugs in your code, higher code coverage can help lower the chances that your product will have bugs in production.
Don’t fret about setting 100 percent coverage as a goal. Start low at, say, 30 percent, and then work toward a minimum threshold of 70 percent to 80 percent over time. If you set a minimum percentage goal to have before going to production, your team will be in a good place to ensure quality around your tests.
Setting goals can be especially useful when you integrate code coverage into your CI/CD pipeline. If your test coverage goes down after you create a certain feature, then you know something is wrong. You could have developed a new feature which is lacking testing, or you forgot to add tests to cover a particular pathway in your application after new code was written.
When Your Product Has Long Production Cycles
Many businesses nowadays are deploying their products daily, as they want to leverage the advantages of being able to release new features quickly or to promptly solve issues.
However, this is not the case for every company. It is difficult to update systems that aren’t connected to the internet, and so it makes sense to space releases further apart. For reasons like these, many releases occur at intervals of six months to a year.
If your company is in this position, you must be extra careful with every release you make as errors can’t be fixed quickly. Code coverage acts as an error mitigation strategy. It lets you evaluate the overall coverage of your tests so you can assess whether all your code is covered before a release.
When Your App Has Critical Services
Even if people’s lives do not depend on your software, the quality of your most critical services is still extremely important. Think of the transaction services in a banking app. A failure in this area could cause you and your clients to lose money, eventually leading to a loss of reputation and customers.
Code coverage can help an organization avoid such blunders. It lets you identify gaps where code is not being tested properly. You could also use it to enforce higher testing standards for mission-critical services.
Conclusion
In the modern software market, it’s critical that your application be well tested and reliable, which makes having a robust test suite essential to the success of any product. Code coverage can help you identify areas in your testing that may need improvement.
If you’re ready to adopt code coverage for your organization, be sure to check out Codecov. As long as your testing tool produces coverage reports in a format supported to Codecov, you will receive status checks on your commits and coverage support for a variety of languages and CI/CDs. You can schedule a demo to learn more about how Codecov can help you and your team deploy with confidence.
