Black Box Test Design Techniques - Equivalence Partitioning and Boundary Value Analysis

 Equivalence partitioning Test Technique

As the name itself says, imply equivalence i.e equal.  Equivalence  partitioning divides data into partitions(equivalence classes). So that all classes/data/members are given equal preference. All the members of the partitions are expected to be processed in the same way.

Valid Class: Valid values are values that should be accepted by the component or system. An equivalence partition containing valid values is called a “Valid Equivalence Class.”

InValid Class : Invalid values are values that should be rejected by the component or system. An equivalence partition containing invalid values is called an “Invalid Equivalence Class.”

Any data can be divided into partitions as much they can/want. However, each value used in one partition can not be used in other partitions. 

Example 1:

Test the age Field which accepts only Age Including Between 18 to 27

In practical terms, it is not possible to cover all values for testing the ranges. So we choose Equivalence partitioning Techniques for choosing the Representatives from Ranges and to cover all areas of Requirement

Minimum Number of Equivalence Partitioning Test cases are 3. 

Equivalence Partitioning Test case 1 : Input Age = 10 { Less than 18} - InValid Class

Equivalence Partitioning Test case 2 : Input Age = 20 { including Between 18 to 27} -Valid Class

Equivalence Partitioning Test case 3 : Input Age = 30 { Greater than 27} - InValid Class

Boundary Value Analysis(BVA)

Boundary Value Analysis is the extension of equivalence partitioning in which values near Boundaries are used for testing.

Boundary value testing selects the input values as 

1. Minimum

2. Just above the Minimum

3. Nominal Value

4. Just Below the Maximum

5. Maximum

Boundary values Techniques takes values from both valid and invalid Boundaries.

Example 1:

Test the age Field which accepts only Age Including Between 18 to 27

Boundary value Test case 1 : Input Age = 17 { Less than 18} - Invalid Boundary

Boundary value Test case 2 : Input Age = 18,19,26,27 { including Between 18 to 27} -Valid Boundary

Boundary value Test case 3 : Input Age = 28 { Greater than 27} - Invalid Boundary

In Most cases, Boundary value Analysis and Equivalence Partitioning are used together to Meet Specifications/Requirements for Higher coverage.

Advantages of Boundary value Analysis and Equivalence Partitioning:

1. Saving time and cost in testing

2. It allows you to find more defects while testing rather than using some random values.