Hi,

How do you do BVA for range between 10-20?

This question was posed to me by a inteviewer. As per theory, i told
him 9,10,11 (min-1,min,min+ 1)and 19,20,21(max- 1,max,max+ 1)
values will be tested.Then he questioned the rationale behind testing
11 and 19 .he told me that if 11 passes surely 19 too would pass.for
which i was unable to reply.

Friendz,can anyone explain BVA clearly?????
Any docs on this subject would be very helpful.

Thanx,
vb

Your initial answer was correct. He tried to confuse you by saying that if 11 passes then 19 will also pass. It is not necessarily true.

The logic behind BVA is that, for the reasons unknown, it is generally observed that the values near the boundaries (10 and 20 in above example) would fail more often then not. That is the reason BVA technique is followed.

But we need not apply BVA on above example, coz without BVA we have to check 11 values (10 to 20) and with BVA we are checking 6 values (9,10,11,19,20,21). The difference is that of only 5 more numbers. May be a matter of few more seconds of automation testing for average sized iteration.

__________________
Lack of WILL POWER has caused more failure than
lack of INTELLIGENCE or ABILITY.

-sutnarcha-

The boundary value analysis can have 6 text cases.

n, n-1,n+1 for the upper limit and
n, n-1,n+1 for the lower limit.

But as you know we use equal class partitioning also for minimizing our test cases.

In your example, as per BVA, there are 6 test case data,
9,10,11 and 19,20,21.

But we will test for 9,10 and 20,21 only.

Because these 4 test case is sufficient to test the range, because we get both positive and negative test case from these 4 values.

__________________
Brijesh Jain
brijesh.tester@yahoo.co.in
http://softwaretestingexpertise.blogspot.com

hi
i think that is a good explanation by jain brijesh to reduce the effort of testing by reducing one test case...
in BVA we follow equivalence class patitioning.....
suppose you had to test the range 10-20...it means inclusive of the the boundary values...

so there are three equal patitions you can do
a) for values less than the lowest value in the range....
b) for values falling inside the range.....
c) for values more than the highest value of the range...

so we can write the test cases (both +ve and -ve ) pertaining to the partions mentioned above....which will derive six test cases
and as systems are prone to making mistakes at the boundaries we will have to include the test cases checking the boundaries too....
i.e. two test cases(+ve and -ve)....each for 10 and 20...which will make the total to 10...
while executing however, for each partition we will place our negative test case first for every partition.....so as to save our effort of going through the application again and again......

and the interviewer probably said right as you have checked the value falling between the range once by executing two test cases for partition (b) there is no need to check for all values falling in the range.....test case which is passing on...11 can pass 19 too however system cant be trusted...so it is better to test it for 19...as i mentioned earlier that the systems are prone to making mistakes aat boundaries...it is better that jus for saving the effort of executing one test case we do not make assumtions that the system will pass any value falling within the range...so when we choose values for our partion (b) it is better to include both 11 and 19........

less than 10|at 10|inside the range(11,19)|at 20|more than 20.....

thanks!!

remember we always check for
a) the things which the system is supposed to do, as well as
b) the things which the system is not supposed to do......

and if we have checked the system for (b) then it necessarily doesnt mean that it will do what it is supposed to do

Can you give me some examples with answers, as to how to identify the number of test cases to write w.r.t to EP and BVA?

Hi there,

For this question, I think there is no much difference between 11 and 19 to be defined as check the boundary point values 10 and 20 respectively. I think for BVA testing there should be 5 ranges (not 6) for this question: <10, =10, >10 and <20, =20, >20, and then we should pick out the typical data from each 'range'. It does matter you choose a value equal to boundary value+1 (-1) or not, but does matter that you can define the right data 'range'.

thx