Test cases for pen

1. Verify the functionality of writing the pen
2. verify the color of writing
3. verify of which material the pen is made
4. verify the size of refill so that it can placed correctly
into the pen
5. verify the cap is fitting correctly
etc.....

correct me if I am wrong

Adding to above test case:-
- friction/smothness of writting by the pen.
- how long it could write.
- whether reusable.
- specific position to place the pen (applicable if it 
leaks).
Many more can be added.

Test case for yahoo sign in page

1)Verify userid field.
2)verify password field.
The above testcases to check whether the editboxes 
accepting data or not.

3)Enter valid userid and password and click on signin 
button.
4)Enter valid userid and invalid password(viceversa)and 
click on signin button
An error message should be displayed
5)Enter valid userid and leave the passwordfield blank
(viceversa)(for invalid data also) and click on signin 
button.