This is my first time using Equivalence Class Partitioning. I have decimal input fields that I need to test. I am going to explain my understanding of the ECP method and provide you with my test cases, so please correct me if I'm wrong.

One field is of the type decimal(5, 2). So from my understanding of ECP is that I define class of valid and invalid numbers, and then use one valid case from the valid class, and two invalid cases from the invalid class.

So going with my example, the valid class is from 111.11 to -111.11 The invalid class is 1111.11 to -1111.11. So for me I decided to use this case for valid input: input1= 111.11 and These cases for invalid input: input1= 1111.11 input2= -1111.11.

Am I doing it right? or is my understanding is wrong?

1 Answer 1


Your understanding is incomplete and your example is misleading.

Equivalence partitioning does not divide inputs into two categories only, e.g. valid and invalid. It can divide inputs into as many classes as you see fit, e.g.

  • Valid inputs that are too big
  • Valid inputs that are big
  • valid inputs that are common
  • Invalid inputs that are common
  • Invalid inputs that are small
  • Invalid inputs that are too small

As long as a partitioned class share a distinct characteristic.

Your example is misleading, how can you define the valid class as from 111.11 to -111.11 and your invalid class as from 1111.11 to -1111.11.

  • Your invalid class includes your valid class?!?!
  • Partitioned classes need to be mutually exclusive.
  • Yes thats true. My example is misleading. But I am trying to get my head around the ECP, can you help?
    – l1ghtblue
    Commented Jun 8, 2017 at 17:15
  • @l1ghtblue, istqbexamcertification.com/…
    – Yu Zhang
    Commented Jun 8, 2017 at 21:07

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