# What is code coverage?

**Methodology** that quantitatively measures how comprehensive a code base's tests are. 

Increasing code coverage often increases stability and reduces bugs.

#### Formula:

* Total number of non-syntax lines with tests / total number of non-syntax lines

#### When to care about code coverage?

* Your product has users and those users might leave if they are affected by bugs
* You are working with developers that aren't immediately trustworthy like contractors/interns
* You are working on a very large code base with many testable components

{% hint style="warning" %}
**Common mistake - too many tests for uncertain features**
{% endhint %}