For almost all application we need to find the boundary of the features inside the application under test and it can be done by Boundary Value Analysis (BVA).
Boundary Value Analysis is a test design technique which does a selection of test case that exercises bounding values.
Boundary Value Analysis is a complement to Equivalence Class Partitioning (ECP). BVA selects test cases at boundary/edge of an equivalence class.
Values considered for Boundary value analysis are
- Upper boundary/Limit
- Lower boundary/Limit
- Upper boundary +1
- Lower boundary -1
boundary value analysis is one of the important criteria during testing the application. as you can find more and more defects at the boundary.
Examples: during interview this most common questions
1) Write BVA test cases for Test box where textbox has min char. the limit is 4 and max char. limit 10
Answer: if you look at above listed considered values for BVA, the answer will be there will 4 test cases, I will test it for values, 4 (Lower limit), 10 (upper limit), 11 ( upper limit +1) and 3 ( lower limit +1).
2) Write BVA test cases for Textbox which has fixed input size, say 5 char.
Answer: In this condition, look at the word FIXED, so there lower and upper boundary conditions are same, as value I need to enter is fixed. so my test cases will be 3 and values will be 5( upper and lower limit), 4 ( lower limit -1), 6 (upper limit +1)
I hope this will clear your thoughts about the boundary value analysis.