boundary value analysis is concerning about checking the
boundary values that is minimum and maximum values  for ex:
for checking values of 20to 30  we have to take minimum 20
an d maximum 30 not more than that. take another ex:  if you
checking for login page you have to enter password atleast 6
butless than 6

Boundary value analysis is an technique used in black box
testing for selection of test data's for valid and invalid
values it is divided as upper boundary lower boundary and on
boundary ex:take a password field wch accepts 5 digits so do
+/- 5 we get diff BV for upper boundary & lower boundary