Add tests

_sidebar.md

@@ -11,6 +11,7 @@
 - [Database](categories/database.md)
 - [Application](categories/application.md)
 - [Web Scraping](categories/web-scraping.md)
+- [Testing](categories/testing.md)
 - [Devops](categories/devops.md)
     - [Docker](categories/devops/docker.md)
     - [Incident Management](categories/devops/incident.md)

categories/testing.md

@@ -0,0 +1,6 @@
+Testing
+
+
+# Test layers
+
+(https://raw.githubusercontent.com/wahyd4/knowledge-mind-mapping/master/assets/images/test_layers.png)