diff --git a/README.md b/README.md
index a93fa40..e4df2a5 100644
--- a/README.md
+++ b/README.md
@@ -123,6 +123,7 @@ There are some free books available, including:
 
 * [Testing Strategies in a Microservices Architecture](http://martinfowler.com/articles/microservice-testing/) (Martin Fowler) is an awesome resources explaining how to test a service properly.
 * [A Quick Puzzle to Test Your Problem Solving](http://www.nytimes.com/interactive/2015/07/03/upshot/a-quick-puzzle-to-test-your-problem-solving.html?_r=0)... and a great way to learn about confirmation bias and why you're mostly writing positive test cases.
+* [The test pyramid](http://martinfowler.com/bliki/TestPyramid.html)
 
 ### Writing for performance