doc: update requirement of lab2

Author: TaiYou-TW

lab2/README.md

@@ -2,15 +2,18 @@
 
 ## Introduction
 
-In this lab, you will write unit tests for functions implemented in `main.js`. You can learn how to use classes and functions in it by uncommenting the code in it.
+In this lab, you will write unit tests for functions implemented in `main.js`. You can learn how to use classes and functions in it by uncommenting the code in it. (But remember don't commit them on GitHub)
 
 ## Requirement
 
 1. Write test cases in `main_test.js` and achieve 100% code coverage. Remember to use Mock, Spy, or Stub when necessary, you need to at least use one of them in your test cases. (100%)
 
 You can run `validate.sh` in your local to test if you satisfy the requirements.
 
-Please note that you must not alter files other than `main_test.js`. You will get 0 points if you modify other files to achieve requirements.
+Please note that you must not alter files other than `main_test.js`. You will get 0 points if
+
+1. you modify other files to achieve requirements.
+2. you can't pass all CI on your PR.
 
 ## Submission