# 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 \[Obsoletes\]](/files/-McNLt7D7WVo6LT8tKru)

{% 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 %}

![](/files/-Ma7o48WN0C1t_Id8USK)

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](/files/-McNIaclZb5da0cAYSrH)

## 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.


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