Boundary Value Analysis(BVA)

Boundary Value Testing is the most well-known and simple technique of test design, which helps the tester choose the most effective values ​​from the ranges of values. This technique is applicable at all levels of testing – unit, integration, system, and system-integration test levels.

We consider the steps of using of the equivalence classes technique:
1.Determining the range of values ​​(usually, the equivalence class).
2.Determination of the boundary range.
3.Creating three test cases for each boundary – one that checks the border value; second that checks the value below boundary; and the third that checks the value above boundary.

An example of the ‘upper’ and ‘lower’ boundary values. If the boundary is $ 3, the “lower” boundary will be $ 2, and the “upper” – $ 4. If the boundary is $ 2.00, the “lower” boundary will be $ 1.99, while the “upper” $ 02.01, etc.
Let’s discuss this technique on an example.
Returning to our pencils (see Equivalence Class Testing), the pens vary in price depending on the ordered quantity:
1 – 100 – $ 10. the pens;
101 – 200 – $ 9. the pens;
201 – 300 – $ 8 on the pens, etc.
With each one hundred, the price is reduced by $ 1.

The maximum available amount is 500 pcs. Boundary value analysis are very interested in the boundaries of the values intervals, because it is “analysis of the boundary.” Using the method of equivalent partitioning, the following classes were identified:
1. Valid values ​​are from 1 to 100;
2. Valid value: 101 to 200;
3. Valid value: 201 to 300;
4. Valid value: 301 to 400;
5. Valid value: from 401 to 500;
6. Invalid value:> 500 pieces;
7. Invalid value <=0;
8. Invalid value: a float from 0 to 500;
9. Invalid value: a negative number;
10. Invalid value: a collection of letters;
11. Invalid value is an empty string.
It’s time to take on boundary values ​​of these classes. You should take not only the limiting value, but also retreat one step up / down (on the tiniest step as possible). We obtain for the above written classes:
1. 1; 0; -1;
2. 99; 100; 101;
3. 199; 200; 201;
4. 299; 300; 301;
5. 399; 400; 401;
6. 499; 500; 501;
Thus, we get to 3 values ​​for the boundaries and take one value from “bodies” of the equivalence classes for a total of 21 + 11 = we take 32 values for verifying. M-m-m-m-m it is more than 11, but much less than 500. Yes, and we check not only the valid values, but also invalid! But it’s only two techniques of … to be continued …