Black box testing method - Equivalence partitioning - Software Process Improvement

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• Nirja Shah   -Posted on 26 Oct 15
  Equivalence partitioning
  - It is a software testing technique that divides the input data of a software unit into partitions of equivalent data from which test cases can be derived.
  
  - In principle, test cases are designed to cover each partition at least once.
  
  - This technique tries to define test cases that uncover classes of errors, thereby reducing the total number of test cases that must be developed.
  
  - An advantage of this approach is reduction in the time required for testing a software due to lesser number of test cases.
  
  - It is typically applied to the inputs of a tested component, but may be applied to the outputs in rare cases.
  
  - These partitions are usually derived from the requirements specification for input attributes that influence the processing of the test object.
  
  - The fundamental concept of ECP comes from equivalence class which in turn comes from equivalence relation.
  
  - A software system is in effect a computable function implemented as an algorithm in some implementation programming language.
  
  - Given an input test vector some instructions of that algorithm get covered, others do not.
  
  - This gives the interesting relationship between input test vectors:- _aC_b is an equivalence relation between test vectors a,b if and only if the coverage foot print of the vectors a,b are exactly the same, that is, they cover the same instructions, at same step.
  
  - This would evidently mean that the relation cover C would partition the input vector space of the test vector into multiple equivalence class.
  
  - This partitioning is called equivalence class partitioning of test input.
  
  - If there are N equivalent classes, only N vectors are sufficient to fully cover the system.

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