Why is Test Coverage an Important Part of Software Testing?

Vipinraj Nair
6 min readAug 26, 2021


There is no second opinion in acknowledging the importance of software testing. We all know it is crucial to test the software to verify whether it meets the requirements and ensures it is error-free.

Yes, when you develop software, errors may appear in any phase of the life cycle. So, software testing comes in place to identify bugs, gaps, or any missing requirements compared to the actual needs.

However, one of the challenging decisions is knowing when to stop testing? How much is good testing? Do you need to test 100% of your application? Or do you need to focus on the areas that have more problems? Is it wise to allocate your resources uniformly throughout the application or focus only on those most critical modules?

Is there any metric for that? There comes the need for test coverage. Test coverage is an essential indicator of software quality and an inevitable part of software maintenance.

This blog will give you insights into test coverage and its techniques and why you should leverage them to make the most out of your testing approach. Let’s get started.

What is Test Coverage?

Test coverage is a metric in software testing that evaluates whether your test cases cover the application code and how much code you exercise when you run those test cases. Thus, test coverage helps to evaluate the effectiveness of your testing by offering data on various coverage items.

Ultimately, test coverage is a beneficial tool in identifying the untested parts of a codebase. It allows test generators to monitor the testing quality and directs them to create test cases to cover the untested areas.

Test Coverage Techniques:

1) Product Coverage

As the name indicates, product coverage is nothing but test coverage from a product perspective. In other words, ask yourself which areas of the product you have tested?

Let’s assume that you have to test a simple application like a calculator. Though you must check the essential functions like four arithmetic operations, that is not enough. You have to consider other factors also while testing the calculator app.

You have to go the extra mile in testing various scenarios, like how well the calculator handles large numbers. Or, what if the user did something unusual like pasting special characters into the text field?

You have to test your product for multiple scenarios else you can’t claim your application has complete product coverage.

2) Risk Coverage

Risk coverage is all about assessing the risks involved in an application and testing them in detail. You can list out all possible risks that may happen in the application and check them appropriately.

For example, let’s assume you have to test a food-delivery app. The user chooses the restaurant and food preferences in the app and pays via the payment gateway integrated with the app. One default risk here is that the users go offline when they are in the payment process.

In that scenario, how will your application behave? Likewise, you have to ask yourself the relevant risk factors involved in the application and check them.

3) Boundary Value Coverage

Boundary value analysis is a part of software testing that allows the tester to create test cases needed for the input field. For instance, consider you have a feature that can take numbers as input. However, it should only accept numbers from 0 to 50. In that scenario, you have to ensure that you test the boundaries appropriately.

So, you can test the application by giving numbers less than 0 like negatives and higher numbers above 50. That way, you can reduce the errors in your application precisely. Boundary coverage ensures testing such boundaries across the application.

4) Requirements Coverage

Requirements coverage is crucial of all the techniques we discussed today. Of course, even if your application is error-free and performs well, what if it did not meet the user’s requirements? Again, it is a big problem.

Consider, you market your app with specific features. But, your app did not have those features. That way, no one will prefer the app. So, it is highly crucial to create a requirement list when creating the test plans. Thus, you can test whether your app meets all requirements.

Nevertheless, requirements coverage is the most fundamental and essential technique. It makes sure your app fulfills all requirements. After all, that is the whole logic behind software development.

5) AI- Aided Test Automation

AI-aided test automation is the advanced technique of all the above-discussed test coverage techniques. AI-aided test automation uses automation tools that make your testing approach to the next level.

These AI-aided tools come with test suites that apply machine learning to learn with each execution. AI even enables self-correcting test cases, easing the burden of test maintenance. Thus, you can have a robust test suite that provides your app with premium test coverage.

Why is Test Coverage an Important Part of Software Testing?

1) Find Bugs and Rectify them at Early Stages

You can find any gaps in requirements, test cases, and defects at a very early stage of your product development. Hence, you can avoid any delays, reworks and can offer a high-quality product.

2) Create more Test Cases to Ensure Better Coverage

Test coverage allows you to create more test cases, encouraging you to have premium coverage. That, in turn, leads to fewer defects and less work at later stages. Above all, you can improve your customer experience with an optimal product.

3) Remove Unwanted Test Cases

Test coverage helps you identify the unnecessary test cases that are not relevant to your current project. Thus, your developers can eliminate those test cases and make the overall code lighter.

4) Own Better Control over Your Project

Test coverage enables you to have better control over the resources during the entire product development lifecycle. You can save time and cut costs as you can find and fix defects earlier and faster. Ultimately, you can have direct control over the project.

5) Efficient Testing Cycles

With test coverage analysis, you can prevent defect leakage effectively. Plus, test coverage helps in regression testing, prioritizing test cases, augmenting and minimizing test suites. All of these will lead to smooth, flawless, and efficient testing cycles.

6) Higher ROI

As test coverage allows you to identify defects early, you will have very few bugs at the production stages. Thus, you can utilize all the resources appropriately and not on addressing the defects and issues. So, test coverage will have a significant impact on the ROI for sure.

How to Calculate Test Coverage?

You can calculate test coverage with a relatively easy formula. You can take the number of lines covered by a test and divide it by your application's total number of lines.

Test Coverage = (No of lines that have been tested/Total No of lines of code) x 100

So, your app has 1000000 lines of code, and 400000 of those are exercised by at least one test case; your test case is 40%.

Though it sounds trivial, figuring out the number of lines in the app currently under test can be challenging.

Wrapping Up

Hands-down software testing is as crucial as software development. After all, you need to test the software to know whether it is working as intended. As easy as it sounds but, figuring out a suitable testing strategy has always been an overwhelming task.

One of the prime challenges most professionals face is how to decide what and how much to test. However, test coverage techniques are here for your rescue to help you make the most out of your tests.

Test coverage techniques help you constantly track the quality of your tests and cover areas that are not validated. You can choose to test your application depending on risk, product, requirements, etc, and refine your end product efficiently. Additionally, with AI and self-correcting test cases, you can handle test maintenance even more at ease.

Ultimately, test coverage allows you to do software testing effectively, encouraging you to offer high-quality applications, increased customer satisfaction, and a high ROI.