diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 6596478f9..ba0075922 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -86,6 +86,7 @@ We can always use more test coverage.
 * **Use the same coding style as the one used in this project**.
 * **Documentation:** If your PR adds or changes any public properties or methods, you must retain the old versions preceded with `[Obsolete("Describe what to do / use instead")` attribute wherever possible, and you must update any relevant pages in the /docs folder.  It's not done until it's documented!
 * **Welcome suggestions from the maintainers to improve your pull request**.
+* **Include unit tests for new code** Unit test for new code helps us check if it works. See the [Unity Test Runner](https://docs.unity3d.com/2018.4/Documentation/Manual/testing-editortestsrunner.html) for more information about running tests in unity.
 
 Please follow our coding conventions (below) and make sure all of your commits are atomic (one feature per commit). Rebase your pull requests if necessary.