diff --git a/coursepages/spd/README.md b/coursepages/spd/README.md
index aa9c9da..96b1d44 100644
--- a/coursepages/spd/README.md
+++ b/coursepages/spd/README.md
@@ -83,6 +83,10 @@ This course has really integrated with the programming languages it uses. We sug
 
 The programs in this course embed pictures and rich-text blocks in the code, which means, the files cannot be opened by other IDEs. While it is possible to prepare the starter files for use with other IDEs, you need Dr. Racket for that, and the time needed to do that can be better utilized in learning the concepts taught by the course.
 
+### How do I test functions which are supposed to output random values?
+
+You can use `check-random` to test those functions. You can [learn more about it here](https://docs.racket-lang.org/htdp-langs/beginner-abbr.html#(form._((lib._lang%2Fhtdp-beginner-abbr..rkt)._check-random))). It is needed for the Space Invaders project.
+
 ## Credits
 
 The problem starter files and the space invaders instructions were taken from the course ["Systematic Program Design" on Edx](https://learning.edx.org/course/course-v1:UBCx+SPD1x+2T2015), licensed under [CC BY-NC-SA](https://creativecommons.org/licenses/by-nc-sa/4.0/) license.