Black Box Testing Techniques

The below three are black box design techniques:

o   Equivalence Partitioning

o   Boundary Value Analysis

o   Error Guessing

Equivalence Partitioning:

Equivalence partitioning is the black box testing technique.

This technique helps us to divide the set of test condition into a partition that can be considered the same condition.

Advantage of this technique is to reduce required time by testing all the required coverage of the software with fewer test cases than many test cases.

For Example:

Assume, text box called ‘age’ exist in software, as per function it should accept 1 to 100 as age limit, it should not allow to accept less than 1 and numbers greater than 100.

Conditions	Without equivalence partitioning	Using equivalence partitioning
Should accept 1 to 100 Should not accept negative values (-1,0) Should not accept (> 100)	It’s required to write 100 + test cases. Test case 1 : To test input number ‘1’, Test case 2:  To test input number ‘2’, Test case 3:  To test input number ‘4’…. So on up to 100 Test case 101: For >100 Test case 102: For < 1	It’s enough to write three test cases to test all the condition using equivalence partitioning. Test case 1: One valid input from 1 to 100. Test case 2: One invalid input < 1. Test case 3: One invalid input > 100.

Boundary Value Analysis:

Boundary value analysis is a black box testing technique is used to test the boundary values rather than testing the interior values.

For Example:

Assume, text box called ‘age’ exist in software, as per function it should accept 1 to 100 as age limit, it should not allow to accept less than 1 and numbers greater than 100.

Conditions	Without Boundary Value Analysis	Using Boundary Value Analysis
Should accept 1 to 100 Should not accept negative values (-1,0) Should not accept (> 100)	It’s required to write 100 + test cases. Test case 1 : To test input number ‘1’, Test case 2:  To test input number ‘2’, Test case 3:  To test input number ‘4’…. So on up to 100 Test case 101: For >100 Test case 102: For < 1	It’s enough to write three test cases to test all the condition using equivalence partitioning. Test case 1: Input Exact boundary value 1 and 100. Test case 2: Below the extreme boundary edges of input value 0 and 99. Test case 3: Above that extreme boundary edges of input value 2 and 101.

Error guessing :

Error guessing is the black box design technique, which focuses on identifying the defects without having formal documentation. This technique usually performed by the experience tester with enough knowledge on functionality.