Category: KPIs Library.

Test Coverage and Why It’s Important

Testing a system before it’s rolled out is a matter of course. You’ll find no professional today who would ever suggest you don’t, but that is just one part. Before you report the results of a test, you need to ensure that the test is fully effective. For example, consider you take a blood test to see if you are susceptible to certain medicinal side effects. The results come back all clear, so you go ahead and ingest the medicine, but you end up feeling side effects you didn’t expect. You find that the blood test you took was not fully prepared for real-life application and, as such, couldn’t predict the effect it would have on you. That is what test coverage is for, only for coding. It ensures the tests you implement on a system are effective and fully affect the system when implemented.


By failing to prepare you are preparing to fail

Benjamin Franklin

What is Test Coverage?

Test coverage is a software testing metric that shows how much code gets checked during testing. Consider the case where you create a simple calculator program to help with your work. The code accounts for all the functions it needs, and your test shows it. But you don’t know whether it would work on different operating systems or devices. Test coverage ensures multiple different permutations and combinations are accounted for in your test.

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Well-implemented test coverage can be used to give a quantifiable result on how effective your test is. In business, it can be used as a Key Performance Indicator (KPI). Businesses that sell software would need to use test coverage to ensure that their product would work well in real-life scenarios. While it can be adapted into different versions, there is one basic formula you can refer to for test coverage:

Test coverage = (Lines of Code Covered by Tests / Total Lines of Code) * 100

If you need to test 1000 lines of code, but your test only tested 500, that would mean your test coverage is 50%.

The Uses for Test Coverage

Test coverage can also be very versatile, depending on what scenario you are attempting to apply it to:

  • Product Coverage: How much of a product is covered?
  • Risk Coverage: How risky an application is?
  • Requirements Coverage: How many requirements were met?
  • Compatibility Coverage: Whether your program is compatible with different browsers and devices?
  • Boundary Value Coverage: Whether the application meets the minimum and maximum boundaries?
  • Branch Coverage: Whether all the branches and decision points are executed?

A Well-Done Test Coverage has the Following Benefits

Effective test coverage ensures that all critical application paths are evaluated, leading to higher quality software and a reduced risk of defects post-release. It also provides valuable insights into the software’s reliability and performance, fostering confidence in its deployment and usage.

  • Identify defects earlier
    Whatever parts of your code were not tested helps you narrow down where the errors are and saves you from mistakes later.
  • Increased return on investment
    Fewer defects mean fewer complaints, thus less time and money spent later making further corrections for the customer, increasing profits.
  • Robust tests
    Test coverage unveils the paths your tests take when implemented and shows exactly which areas need to be accounted for in the future.
  • Improved control
    With greater information about how well your program operates, you save time and display greater results in your work.

Using Test Coverage with OKRs

Objectives and Key Results (OKRs) can measure performance, but their primary purpose is to be a framework for progress. OKRs are used aspirationally in the sense of encouraging employees to break out of their “business-as-usual” cycle. Therefore, what’s important is not always finding success but rather the creative attempts to do so.

Here’s how you could use test coverage in forming your OKR

Objective: Increase Test Coverage to 85% over 3 months

KR 1: Prioritize all reported defects within 24 hours by severity level.
Initiative 1: Conduct swift triage of all reported defects to classify them accordingly.
Initiative 2: Establish and communicate clear criteria for each defect category.
Initiative 3: Implement an automated system for rapid defect prioritization.

KR 2: Create 3 more varied tests based on initial test coverage results
Initiative 1: Analyze initial test results to find testing gaps.
Initiative 2: Develop three new tests to cover these gaps.
Initiative 3: Review and update tests as needed.

KR 3: Identify common mistakes from previous projects and make a comprehensive checklist
Initiative 1: Review past projects for recurrent mistakes.
Initiative 2: Gather team insights on common mistakes.
Initiative 3: Create a checklist to avoid these mistakes in the future.


After you conduct test coverage, your next actions can be much better planned out. You would be well aware of which dead code to remove, which code is redundant, and which instances is your code not compatible at all. Combining it with an OKR encourages your coders to be more attentive and meticulous in their work while also providing them clarity in which direction they should be working. Keep in mind though that the best OKRs are the ones made with input from your team, and who would know test coverage better than your coders themselves?

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