Test setup flow

README.md

@@ -71,6 +71,12 @@ We prepared a [wiki page](https://github.com/onevcat/Kingfisher/wiki). You can f
 
 I want to keep Kingfisher lightweight. This framework will focus on providing a simple solution for downloading and caching images. This doesn’t mean the framework can’t be improved. Kingfisher is far from perfect, so necessary and useful updates will be made to make it better.
 
+### Developments and Tests
+
+Any contributing and pull requests are warmly welcome. However, before you plan to implement some features or try to fix an uncertain issue, it is recommended to open a discussion first. 
+
+The test images are contained in another project to keep this project repo fast and slim. You could run `./setup.sh` in the root folder of Kingfisher to clone the test images when you need to run the tests target. It would be appreciated if your pull requests could build and with all tests green. :)
+
 ### About the logo
 
 The logo of Kingfisher is inspired by [Tangram (七巧板)](http://en.wikipedia.org/wiki/Tangram), a dissection puzzle consisting of seven flat shapes from China. I believe she's a kingfisher bird instead of a swift, but someone insists that she is a pigeon. I guess I should give her a name. Hi, guys, do you have any suggestions?