Tips to design test data before executing your test cases

Tester should check and update the test data before execution of any test case. In this article I will provide tips on how to prepare test environment so that any important test case will not be missed by improper test data and incomplete test environment setup.What do I mean by test data?

If you are writing test case then you need input data for any kind of test. Tester may provide this input data at the time of executing the test cases or application may pick the required input data from the predefined data locations. The test data may be any kind of input to application, any kind of file that is loaded by the application or entries read from the database tables. It may be in any format like xml test data, system test data, SQL test data or stress test data.

Preparing proper test data is part of the test setup. Generally testers call it as testbed preparation. In testbed all software and hardware requirements are set using the predefined data values.

If you don't have the systematic approach for building test data while writing and executing test cases then there are chances of missing some important test cases. Tester can't justify any bug saying that test data was not available or was incomplete. It's every testers responsibility to create his/her own test data according to testing needs. Don't even rely on the test data created by other tester or standard production test data, which might not have been updated for months! Always create fresh set of your own test data according to your test needs.

Sometime it's not possible to create complete new set of test data for each and every build. In such cases you can use standard production data. But remember to add/insert your own data sets in this available database. One good way to design test data is use the existing sample test data or testbed and append your new test case data each time you get same module for testing. This way you can build comprehensive data set.How to keep your data intact for any test environment?

Many times more than one tester is responsible for testing some builds. In this case more than one tester will be having access to common test data and each tester will try to manipulate that common data according to his/her own needs. Best way to keep your valuable input data collection intact is to keep personal copies of the same data. It may be of any format like inputs to be provided to the application, input files such as word file, excel file or other photo files.

Check if your data is not corrupted:Filing a bug without proper troubleshooting is bad a practice. Before executing any test case on existing data make sure that data is not corrupted and application can read the data source.

How to prepare data considering performance test cases?

Performance tests require very large data set. Particularly if application fetching or updating data from DB tables then large data volume play important role while testing such application for performance. Sometimes creating data manually will not detect some subtle bugs that may only be caught by actual data created by application under test. If you want real time data, which is impossible to create manually, then ask your manager to make it available from live environment.

I generally ask to my manager if he can make live environment data available for testing. This data will be useful to ensure smooth functioning of application for all valid inputs.

Take example of my search engine project �statistics testing'. To check history of user searches and clicks on advertiser campaigns large data was processed for several years which was practically impossible to manipulate manually for several dates spread over many years. So there is no other option than using live server data backup for testing. (But first make sure your client is allowing you to use this data)

What is the ideal test data?

Test data can be said to be ideal if for the minimum size of data set all the application errors get identified. Try to prepare test data that will incorporate all application functionality, but not exceeding cost and time constraint for preparing test data and running tests.How to prepare test data that will ensure complete test coverage?

Design your 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.


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. Use the tips provided in this article to categorize test data to ensure complete functional test cases coverage.

Be creative, use your own skill and judgments to create different data sets instead of relying on standard production data while testing.

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