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Arindam Majumder
Arindam Majumder

Posted on • Originally published at

Understanding Code Coverage in Software Testing


Code Coverage is a very important part of the Software Development Life Cycle. It helps to ensure that tests are covering the most critical parts of our application.

In this article, we'll explore what is Code Coverage, Its importance, How it works, and many more!

So Without delaying further, let's Start!

What is Code Coverage?

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Code coverage measures the percentage of code that is tested. It's a very useful metric to test the quality of the test suite. It is one of the forms of White Box Testing.

A program with high test coverage is more likely to have fewer bugs compared to a program with low test coverage

The Formula of Code Coverage:

Code Coverage Percentage = (Number of lines of code executed)/(Total Number of lines of code in an application) * 100.

Why Code Coverage Matters?

But Why should we care about Code Coverage? What will we get from it?

In this section, we will explore the importance of Code Coverage:

  • It helps us to find the untested code where the potential can be. So by finding them, we can minimize the chances of getting bugs.

  • It helps detect regressions early. By tracking code coverage over time, any drop in coverage can indicate a regression that requires further testing.

  • By detecting the unused it helps to improve the maintainability.

  • It seamlessly integrates with CI/CD pipelines, automating coverage measurement throughout the development lifecycle.

  • It works with a variety of programming languages and platforms like C#, Java, JavaScript, and more. This allows the testing of heterogeneous systems

How Code Coverage Works?

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There are many approaches to measure Code Coverage but overall there are three main ways to measure it.

  1. Instrumentation - The code coverage tool modifies the source code by inserting tracing calls. This allows it to track the executed parts of the code.

  2. Test Execution - The test suite is run against the instrumented code. The tracing calls collect data on which lines, functions, branches, etc. were executed.

  3. Reporting - The code coverage tool analyzes the collected data and generates a report showing the percentage of various coverage criteria that were met.

Levels of Code Coverage:

Several levels of code coverage can be measured to determine how thoroughly your test suite exercises your code:

  1. Statement coverage - This measures the percentage of statements in your source code that have been executed by tests. Simply counting the number of lines executed gives you the statement coverage.

  2. Branch coverage - This measures the percentage of branches in your source code that have been executed. Branches refer to decision points like if-else statements, loops, etc. To achieve full branch coverage, tests must execute every branch at least once.

  3. Condition coverage - This measures the percentage of conditions within branches that have been tested for both true and false. It focuses on individual boolean expressions rather than full branches.

  4. Path coverage - This measures the percentage of possible paths through your program that have been executed. It takes into account the order of execution and all possible paths through the code.

  5. Modified condition/decision coverage (MC/DC) - This is the strongest form of coverage and requires that each condition independently affects a decision outcome. To achieve MC/DC coverage, tests must vary one condition at a time while holding others constant.

There are several tools available in the market to measure the Code Coverage of any Software. Some are given below:

  • Cobertura

  • Clover

  • Gretel

  • Kalistick

  • JaCoCo

  • JTest

  • OpenCover

  • Emma

  • GCT


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Top comments (1)

glowiep profile image
Gloria Lim

Thank you for the levels of code coverage summary! This is helpful