Difference between Black Box Testing and White Box Testing

            I have heard from reader about few terminology of Software Testing. Amongst the list readers asking about the what is meaning of Black Box and White Box testing. They were totally confused on the this Software Testing terminology and who is responsible for doing this type of testing, when it is carried out and what all inputs required to perform such types of testing.

1) Boundary Value Analysis (BVA):

Boundary Value Analysis is the most commonly used test case design method for black box testing. As all we know the most of errors occurs at boundary of the input values. This is one of the techniques used to find the error in the boundaries of input values rather than the center of the input value range.

Boundary Value Analysis is the next step of the Equivalence class in which all test cases are design at the boundary of the Equivalence class.

Let us take an example to explain this:

Suppose we have software application which accepts the input value text box ranging from 1 to 1000, in this case we have invalid and valid inputs:

Invalid Input	Valid Input	Invalid Input
0 – less	1 – 1000	1001 – above

Here are the Test cases for input box accepting numbers using Boundary value analysis:

Min value – 1	0
Min Value	1
Min value + 1	2
Normal Value	1 – 1000
Max value – 1	999
Max value	1000
Max value +1	1001

This is testing techniques is not applicable only if input value range is not fixed i.e. the boundary of input is not fixed.

2) Equivalence Class Partitioning

The equivalence class partition is the black box test case design technique used for writing test cases. This approach is use to reduce huge set of possible inputs to small but equally effective inputs. This is done by dividing inputs into the classes and gets one value from each class. Such method is used when exhaustive testing is most wanted & to avoid the redundancy of inputs.
In the equivalence partitioning input are divided based on the input values:

• If input value is Range, then we one valid equivalence class & two invalid equivalence classes.
• If input value is specific set, then we one valid equivalence class & one invalid equivalence classes.
• If input value is number, then we one valid equivalence class & two invalid equivalence classes.
• If input value is Boolean, then we one valid equivalence class & one invalid equivalence classes.