# Tests

A lot of developers are surprised by how stable Mirror is, compared to what they've used before.

This is not by coincidence. Mirror is **heavily** tested with:

* \> **1400** unit tests
* \~ **80%** test coverage

![\[2021-06-17\] Mirror Test Coverage of 79.6% - including all \[Obsoletes\]](https://462154250-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MGmQrf2z6FL0ZpExPAn%2F-McNKDzdVpiWkUi3AfO3%2F-McNLt7D7WVo6LT8tKru%2F2021-06-17%20-%2079%2C6%20percent%20-%20including%20obsoletes.png?alt=media\&token=9ffc1ed5-cc04-4396-8cef-04f8fe517eb1)

{% hint style="success" %}
As far as we know, **Mirror** has the highest test coverage of any `MonoBehaviour`networking library for **Unity**. 
{% endhint %}

In other words, 80% of our code is **covered with tests** making sure that for the given input, it always produces the correct output. Here is what this means in practice:

* If you **report a bug**, we usually fix it and add a test to guarantee that it **never** happens again. 

  If we **accidentally** introduce a bug, odds are our tests will catch it immediately before you ever encounter it in our game.
* We can **improve** existing functions with confidence. If a rewrite doesn't produce exactly the same output as the previous version, then our tests will catch it.

{% hint style="success" %}
As **rule** **of** **thumb**, encountering a Mirror bug in production simply means that we haven't covered that part of the code with tests yet.
{% endhint %}

![](https://462154250-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MGmQrf2z6FL0ZpExPAn%2F-Ma7nUr0ZLTvEjVVnPKl%2F-Ma7o48WN0C1t_Id8USK%2F2021-05-20_16-06-57%402x.png?alt=media\&token=25adcd7a-52ed-43f0-88bf-710b938d654e)

If you download Mirror from the **Asset Store**, then you don't see those tests because we don't want you to worry about them. They are only on **GitHub**.

## Code Coverage Settings

To reproduce the Coverage results, use Unity's Code Coverage Package and run all of our Edit Mode tests.

![Code Coverage settings](https://462154250-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MGmQrf2z6FL0ZpExPAn%2F-McNIDlulb5k-CJLsfQd%2F-McNIaclZb5da0cAYSrH%2F_SETTINGS_.png?alt=media\&token=39676fd5-736e-497b-8b4d-bef7e45fcb88)

## MirrorTest

If you want to contribute tests or clean up existing ones, please do!

Check out the `MirrorEditModeTest` and `MirrorPlayModeTest` base classes. They provide some convenience functions and setup that we use for most of our tests. For example, Creating a networked object with some network components.