Well actually a good test case is defined as a test case
which has the highest pebablity of finding defects.

yes, shriharsha u r correct but little bit incomplete. u
said that test case which has the highest probability of
finding defects. we have to see that what is requirements we
have generated that level of test cases so that all the
requirements of any application should be included, all
paths  covered ,all functionality of application should be
covered in good test case so that the  paths which is
undiscovered and untested will discovered and tested

Hi All,

A good test case is defined as "The test case has the
ability to find out yet undiscovered error or issue or bug."

Design a good test case is that to cover the requirement
specification (Which is mention in the traceability matrix)
related to the functionality of that module. 
also good test case can test functionality of that module is
correct or not completely.

To design a good & effective test case, following ref 
documents are very much essential:

1. Business Process Model
2. Business Requirement Document
3. Roles & Responsibilities
4. Functional Specifications Document

In certain projects, formal walkthrough of these documents 
will be done to team members. With all these information, a 
tester can design a good and comprehensive testcases.