Boundary value analysis is a type of testing technique in 
Black Box testing. For example, if you are going to test a 
testbox, which accepts value 1 - 100, there is no need for 
you to test with all values from 1 - 100. To minimize your 
testing work, you can minimize with test data.Selecting 
minimum value, minimum value - 1, minimum value + 1, 
maximum value, maximum value + 1, maximum value - 1, we can 
reduce our test data in our example.
so the test data's will be 0,1,2,99,100,101.Instead of 
using 100 values and test, Use only 6 values to test that 
scenario.

bva: it is boundry value analysis. here a range of values 
are given as input to test the application.

A technique that consists of developing test cases and data 
that focus on the input and output boundaries of a given 
function. In same credit limit example, boundary analysis 
would test:
Low boundary +/- one (999 and 1,001)
On the boundary (1,000 and 1,500)
Upper boundary +/- one (1,499 and 1,501)

it is technique to reduce the testing work ( block ox 
testing ) .in boundary value analysis is next step of 
euivalent partition , let us take one exmple .

in the application there is form which suppose to fill by 
customer . In this form there is field say age , user has 
to enter the age , and the requirement document specify the 
range of the field like it accept oly the values fron 16 to 
25 then in boundary valu analysis u can enter the value 

lower range >> 15,16,17 
upper range >> 24,25,26 

in the age field and check the performance of the 
application  .