docs: add Testing section to README

README.md

@@ -4,3 +4,29 @@
 
 **[Online docs and demos (latest master
 build)](https://d2-ci.github.io/ui-widgets/)**
+
+## Testing
+
+Testing is done with cypress & cucumber.
+
+* Run `yarn cypress:run`<br />
+  This will run cypress and exit with either 0 or 1
+
+* Run `yarn cypress:open`<br />
+This will open the cypress gui, which is useful for writing tests
+
+### Recording videos and taking screenshots
+
+When running `yarn cypress:run`, by default no video is recorded and no
+screenshot will be taken.
+* Recording videos can be enabled by supplying the
+`CYPRESS_VIDEO=true` env var.
+* Taking screenshots can be enabled by supplying the
+`CYPRESS_SCREENSHOT=true` env var.
+
+### Storybook stories for testing
+
+Sometimes it's required to add stateful stories to test certain behavior.
+That's why you can add files with the following file name format: `*.stories.testing.js`
+These stories will not be used when generating the docs storybook and can
+contain more sophisticated scenarios for testing.