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What is boundary value analysis ? Explain with suitable example.

• Most of the defects in software products hover around conditions and boundaries. By conditions, we mean situations wherein, based on the values of various variables, certain actions would have to be taken. By boundaries, we mean ―limits‖ of values of the various variables.

• This is one of the software testing technique in which the test cases are designed to include values at the boundary. If the input data is used within the boundary value limits, then it is said to be Positive Testing. If the input data is picked outside the boundary value limits, then it is said to be Negative Testing. Boundary value analysis is another black box test design technique and it is used to find the errors at boundaries of input domain rather than finding those errors in the center of input.

• Each boundary has a valid boundary value and an invalid boundary value. Test cases are designed based on the both valid and invalid boundary values. Typically, we\ choose one test case from each boundary.

• There are three guidelines for boundary value analysis :

1. One test case for exact boundary values of input domains.

2. One test case for just below boundary value of input domains .

3. One test case for just above boundary values of input domains .

• Some examples of Boundary value analysis concept are:

  One test case for exact boundary values of input domains each means 1 and 100

  One test case for just below boundary value of input domains each means 0 and 99.

  One test case for just above boundary values of input domains each means 2 and 101.

  For Example: A system can accept the numbers from 1 to 10 numeric values. All other numbers are invalid values. Under this technique, boundary values 0, 1,2, 9,10,11 can be tested.

  Another Example is in exam has a pass boundary at 40 percent, merit at 75 percent and distinction at 85 percent. The Valid Boundary values for this scenario will be as follows:

  49, 50 - for pass

  74, 75 - for merit

  84, 85 - for distinction

  Boundary values are validated against both the valid boundaries and invalid boundaries.

  The Invalid Boundary Cases for the above example can be given as follows

  0 - for lower limit boundary value

  101 - for upper limit boundary value

  Boundary value analysis is a black box testing and is also applies to white box testing.

  Internal data structures like arrays, stacks and queues need to be checked for boundary or limit conditions; when there are linked lists used as internal structures, the behavior of the list at the beginning and end have to be tested thoroughly.

  Boundary value analysis help identify the test cases that are most likely to uncover defects.