diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 548e7df..ab89d8e 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -37,8 +37,11 @@ You can contribute in many ways:
   ```shell
   $ py.test
   ```
+6. If execute py.test and always collect 0 items, then you can try to run
 
-6. Commit your changes and push your branch to GitHub::
+  if your install success and execute just like you expect, then you can suggest that you have already pass the test.
+
+7. Commit your changes and push your branch to GitHub::
 
   ```shell
   $ git add .
diff --git a/PyBeacon/PyBeacon.py b/PyBeacon/PyBeacon.py
index a5ae11a..e1b5c35 100644
--- a/PyBeacon/PyBeacon.py
+++ b/PyBeacon/PyBeacon.py
@@ -84,6 +84,7 @@ def encodeurl(url):
             data.append(s)
             i += len(scheme)
             break
+        """if never match to if, then throw exception."""
     else:
         raise Exception("Invalid url scheme")
 
@@ -111,6 +112,7 @@ def encodeUid(uid):
     ret = []
     for i in range(0, len(uid), 2):
         ret.append(int(uid[i:i+2], 16))
+    """Python's final character"""
     ret.append(0x00)
     ret.append(0x00)
     return ret
@@ -119,6 +121,7 @@ def uidIsValid(uid):
     """UID Validation."""
     if len(uid) == 32:
         try:
+            """UID characters must belong to base 16"""
             int(uid, 16)
             return True
         except ValueError: