Boundary Value Analysis with Examples:

Boundary Value Analysis:

Boundary value analysis is a black box test design technique and it is used to find the errors at boundaries of input domain rather than finding those errors in the center of input.
 Each boundary has a valid boundary value and an invalid boundary value. Test cases are designed based on the both valid and invalid boundary values. Usually is chosen one test case from each boundary.

Boundary value analysis is a next part of Equivalence partitioning for designing test cases where test cases are selected at the edges of the equivalence classes.Boundary value analysis is often called as a part of stress and negative testing. 
 
Lets understand this better now by taking below example:
Test cases for input box accepting numbers between 1 and 1000 using Boundary value analysis:

1) Test cases with test data exactly as the input boundaries of input domain i.e. values 1 and 1000 in our case.

2) Test data with values just below the extreme edges of input domains i.e. values 0 and 999.

3) Test data with values just above the extreme edges of input domain i.e. values 2 and 1001.
Now lets understand it even more simple with the below example:


Question
A program validates a numeric field as follows: values less than 10 are rejected, values between 10 and 21 are accepted, values greater than or equal to 22 are rejected. Which of the following covers the MOST boundary values?
a. 9,10,11,22
b. 9,10,21,22
c. 10,11,21,22
d. 10,11,20,21
Solution
We have already come up with the classes as shown in question 5. The boundaries can be identified as 9, 10, 21, and 22. These four values are in option ‘b’. So answer is ‘B’