In this post, answers for the questions such as what is data driven testing?, how that is important to test automation and how to get that data need to test? are discussed.

What is data driven testing?

In manual testing, using multiple values for the same course of action. In automated testing, using multiple values for same test script.

How this is important to test automation?

Using this method, testers can create highly maintainable test scripts. Additional data can be added to the data source(excel,database) with out modifying the test script.

How to get the needed data?

Using the black-box testing techniques such as Boundary value analysis, Equivalent partitioning and Error Guessing. You may read about these. However, lets see that.

Equivalent partitioning

To test the software with inputs from correct and incorrect data. For example, if you're testing a filed that will accept only positive integers. Positive integer, negative integer and alphabet inputs consists of three portions of data we need to test. With the equivalent partitioning method, one data from each portion is enough. 

Boundary value analysis

In this, data in the boundary of the partition is take. Testing a field which accepts data from 10 to 20 will be tested with 9, 10, 19, 20, 21.

Error Guessing

This method relies on testers knowledge about the product,intuition and past experience.

Now, using these methods, the data is generated. However, we need to answer another question before starting this. Is the necessary to test the product with all these data? Is the possible to reduce the number of combinations needed?

Pairwise testing the answer for that question. Before trying that out, you can take look at Cem Kaner's Impossibility of complete testing. With that background work, you can prepre the data for the minimum set of possibilities needed test. Take a look at this website more info on pairwise testing. You may interested to check James Bach's All Pairs test case generation tool too.