What code coverage is
Code coverage is a measure of how much of a program's code is exercised when its tests run. It is usually expressed as a percentage, indicating what portion of the code the tests actually execute. By showing how much of the code is covered by tests, code coverage helps developers see which parts have been tested and which parts have not been exercised at all.
Why measure coverage
Tests can only catch problems in the code they actually run. If some parts of a program are never exercised by any test, bugs in those parts can go unnoticed. Code coverage reveals these gaps by showing which parts of the code the tests reach. This helps developers identify untested areas and decide where more tests may be needed to improve confidence.
How coverage is measured
Code coverage is measured by tools that track which parts of the code are executed while the tests run. As the tests run, the tool records which lines or sections of the program were reached, then reports the proportion that was covered. This gives a concrete number and often a detailed view of exactly which parts were and were not exercised by the tests.
What high coverage does and does not mean
High code coverage means the tests exercise a large portion of the code, which is generally good. However, it does not guarantee the code is correct or bug-free. Tests might run a piece of code without properly checking its behavior, so coverage shows what was executed, not whether it was tested well. Coverage is a useful indicator, but not a complete measure of test quality.
Using coverage wisely
Code coverage is best used as a guide to find untested parts of a program, rather than as a target to chase blindly. Aiming for reasonable coverage helps ensure important code is tested, but focusing only on the number can be misleading. The real goal is meaningful tests that check behavior, with coverage helping to reveal where tests are missing.
Why it matters
Code coverage is a helpful measure for understanding how thoroughly tests exercise a program. Understanding what code coverage is - the portion of code run by tests, highlighting untested parts - clarifies a common tool in software testing and its limits. For anyone interested in software quality, it is a useful concept to understand.
Related on Skillo
See also: What is unit testing? Explained, What is a bug and debugging? Explained.
Sources
Published date reflects the original event date (2024-06-11). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.
Leave a Reply