Boundary Value Analysis

Boundary value analysis is a technique for test data selection. A test engineer chooses values that lie along data extremes. Boundary values include maximum, minimum, just inside boundaries, just outside boundaries, typical values, and error values. The expectation is that, if a systems works correctly for these extreme or special values, then it will work correctly for all values in between. An effective way to test code is to exercise it at its natural boundaries.


Boundary Value Analysis is a method of testing that complements equivalence partitioning. In this case, data input as well as data output are tested. The rationale behind Boundary Value Analysis  is that the errors typically occur at the boundaries of the data. The boundaries refer to the upper limit and the lower limit of a range of values or more commonly known as the "edges" of the boundary.

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.

Boundary value analysis is often called as a part of stress and negative testing.