Boundary Value Analysis-2

4.0 The Focus of BVA

Boundary Value Analysis focuses on the input variables of the function. For the purposes of this report I will define two variables ( I will only define two so that further examples can be kept concise) X1 and X2. Where X1 lies between A and B and X2 lies between C and D.  

A ≤ X1 ≤ B 

C ≤ X2 ≤ D 

The values of A, B, C and D are the extremities of the input domain. These are best demonstrated by figure 4.1. 

The Yellow shaded area of the graph shows the acceptable/legitimate input domain of the given function. As the name suggests Boundary Value Analysis focuses on the boundary of the input space to recognize test cases. The idea and motivation behind BVA is that errors tend to occur near the extremities of the input variables. The defects found on the boundaries of these input variables can obviously be the result of countless possibilities.But there are many common faults that result in errors more collated towards the boundaries of input variables. For example if the programmer forgot to count from zero or they just miscalculated. Errors in the code concerning loop counters being off by one or the use of a < operator instead of  ≤. These are all very common mistakes and accompanied with other common errors we find an increasing need to perform Boundary Value Analysis.