diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 01582b4..1c3d1e6 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -85,6 +85,7 @@ Ready to contribute? Here's how to set up `pipreqs` for local development.
    You may also need to provide `CA_BUNDLE` as an environment variable or parameter in the `tests/.env.test` file.
 
     $ export CA_BUNDLE="/certs/path/certificates.pem"  # for nix OS
+    
     $ set CA_BUNDLE="C:/certs/path/certificates.pem"   # for win OS
 
 6. Commit your changes and push your branch to GitHub::
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 322f7d9..2c8fdbd 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -17,6 +17,9 @@
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 # fix_SSLError tests.settings (optional) use of .env file
 # alternative would be to set CA_BUNDLE environment variable
+#  $ export CA_BUNDLE="/certs/path/certificates.pem"  # for nix OS
+#  $ set CA_BUNDLE="C:/certs/path/certificates.pem"   # for win OS
+
 python-dotenv
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -25,8 +28,9 @@ flake8
 tox   # only needed in the environment from which tox is run
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-# (optional, personal choice)
+# (optional)
 # vscode settings: "python.formatting.provider": "black",
 #black
+docutils  # reStructured Text support
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/tests/test_pipreqs.py b/tests/test_pipreqs.py
index 1b3ff5e..3b2c49c 100644
--- a/tests/test_pipreqs.py
+++ b/tests/test_pipreqs.py
@@ -6,6 +6,11 @@ test_pipreqs
 ----------------------------------
 
 Tests for `pipreqs` module.
+
+Environment variables used to mock arguments
+e.g.,
+$ set CA_BUNDLE="certificates.pem"     # for win OS
+$ export CA_BUNDLE="certificates.pem"  # for nix OS
 """
 
 import os