boundary value testing..max & min

[harii haran]

hi,
I was reading about boundary value testing..how can we always find min and max values? sometimes we may not know the max value for example if we read from a file, what would be the max value, min would be empty file, max would be ..? any suggestions thanks,

[Jeanne Boyarsky]

Harii,
Boundary value testing usually refers to significant values in your program. Suppose, you have the following code:

if ( num >= 50 && num <= 100 ) { 
//do stuff 
}

You would want to test numbers near 50 and 100. For example, you could test 49, 50, 51, 99, 100 and 101.
Other numbers that are often boundary conditions are -1, 0, 1, and the numbers surrounding the maximum/minimum values a variable can hold.
One boundary condition is an empty file as you pointed out. The others would depend on the logic of the code reading the file.