What is a test data?
In order to test a software or product, we need to enter some data is known as a test data. It is generated by a tester or by automation tools to support testing. It affects the execution of a specific module.Test data may be used for positive and negative testing. Test data used to generate the expected results while testing a given function is a positive test data whereas test data which are used to test the ability of the software to handle unusual and unexpected input. Poorly or ineffectively designed test data may not test all the possible scenarios and can hamper the software quality. Depending upon our testing environment we may need to create or identify test data for our test cases. Typically test data should be generated before we start executing test cases because in many cases creating test data at execution time may takes many pre-steps or test environments configurations which are very time consuming and it may led to exceed testing deadline.

Test Data for Security Testing:-
Security testing is the process to determine that system protects the data from malicious/unauthorized attack. Following topics should be covered to ensure that software is fully secured:-
1) Confidentiality:- All information provided should be held in strictest confidence and should not be shared by outsiders. like if application uses SSL, we should design a set of test data which ensure that encryption is done correctly.
2) Integrity:- Determine that information given by system is correct and we should design test data after taking a deep look at design, code and database.
3) Authentication:- It represents the connectivity of the user. Test data should be designed with different combinations of username and password which validates the authorized user.

Test data for Black Box Testing:-
In blanck box testing, code is not visible to the tester. Test data should be designed to test the meeting of following criteria:- 1) No data
2) Valid data
3) Invalid data
4) Illegal data format
5) Boundary Condition data set
6) Equivalence Partition data set
7) Use case test data
8) State Transition test data set