Preparing proper test data is a core part of “project test 
environment setup”. Tester cannot pass the bug 
responsibility saying that complete data was not available 
for testing. Tester should create his/her own test data 
additional to the existing standard production data. Your 
test data set should be ideal in terms of cost and time. 
Design our test data considering following categories:
Test data set examples:
1) No data: Run your test cases on blank or default data. 
See if proper error messages are generated.
2) Valid data set: Create it to check if application is 
functioning as per requirements and valid input data is 
properly saved in database or files.
3) Invalid data set: Prepare invalid data set to check 
application behavior for negative values, alphanumeric 
string inputs.
4) Illegal data format: Make one data set of illegal data 
format. System should not accept data in invalid or illegal 
format. Also check proper error messages are generated.
5) Boundary Condition data set: Data set containing out of 
range data. Identify application boundary cases and prepare 
data set that will cover lower as well as upper boundary 
conditions.
6) Data set for performance, load and stress testing: This 
data set should be large in volume.
This way creating separate data sets for each test 
condition will ensure complete test coverage.