Test case is a set of conditions or variables under which a
tester will determine if a requirement or use case upon an
application is partially or fully satisfied. It may take
many test cases to determine that a requirement is fully
satisfied.

Test cases are write to check the if user gives i/P to 

the system.Check weather the o/p generated by the system is 

correct.Because of this testing we client will get final 

product with least errors.Generally test cases are 

prepared according to SRS.So it also checks either the 

developer developes the software according to user 

requirements or not.

we can write the test cases, we can produce the good 
quality product and very much satisfied ny the customer

test cases are written to test 
with out test cases also one can test ..but
with test cases there will be some defined steps, 
procedures, expected results etc.., which eventually is the 
desire of a tesing. 
Thus 
....test case is being written to make testing meaning full 
and a systematic approach to conduct testing
....test case is being written to make a process for 
testing 
....test case is being written to make a proof of the work 
done for testing
.... test case is being written to ....etc ...!

Actually,we can say the main activity of devloper is coding 
like this for a tester is to write test cases to verify and 
validate the s/w build.
>Test cases shows what will be the expected and actual 
result before excutiuon of the build.
>It shows what will be the input and output of every 
condition.
>it shows olso how a leyman user come to know about the 
application or can use the application.
>

Test case set of procedure, which we execute your system
find out defects
test id,
test case,
condition,
Action,
Excepted result,
actual result,
result.