Equivalence Partitioning Testing – A Guide

Equivalence Partitioning Testing

Equivalence Partitioning Testing (ECP) is also known as black box testing or identicalness class parcelling. It is a product testing procedure that isolates the test information of the application into each segment. It helps in comparison and helps in determining efficiency of the application.

A benefit of this methodology is that it takes less time for performing testing of a product.

Equivalence Partitioning – A Black Box Testing Technique

The Black Box testing incorporates authenticating the system without having any information and its elementary design. Conducting a test in a black-box way is quite natural. But it brings complications such as the test condition requires hundreds of variations.

Hence, in what way can we constrain the number of variations to low numbers and at the same time get the correct answer? In recent times, some black box technique has evolved to determine the complication in the application. So let’s learn more about this technique.

What is Equivalence Partitioning?

Equivalence class partitioning is a practice through a test condition that is tested by segregation the data into valid and invalid partitions. Here the same set of data is grouped together as a different segment to derive the test results.

Through this technique, the testing becomes more precise. It is perfectly suitable to test objects such as different inputs, outputs, inside qualities, time-related qualities, and interface parameters. This method works on the following assumptions:

●   All the test input variations are treated in the same fashion by the system  

●   If one of the info conditions passes, then the other remaining conditions also passes.

●   If one of the information conditions fails, then any remaining info conditions fails too.

The achievement and adequacy of Equivalence partitioning rely on the above assumptions. In the later part we will further explain this with an example of a gym application process.

How to do Equivalence Partitioning Testing?

Let us explain to you how to conduct this test with an example of filing a gym form.

Consider that you are filing an online application structure for a gym. What are the leading measures for getting an enrolment? One of them is age. If you see, any gym centre form will have age as one of their first fields.

A gym application usually accepts applications from members aged between 14 and 60. If you surpass this age group, your form is either accepted or rejected.

If we need to test this age field, we need to test the fields between 14-60, and rates which are under 14, and more than 60.

It is not difficult to sort out.

Thus, we need to find out different combinations to check if the functionality is working safely. Here are some combinations.

<14 has 13 blends from 0-13, and if you get a negative result, you can add a few more combinations.

14-60 has 45 mixes

>60 has 40 blends (if you take till 100)

In total, here we have 100 combinations. However, it is not possible to test all 100 combinations due to time constraints.

Here is how to get maximum coverage from Equivalence Partitioning.

The First step in Equivalence apportioning is to divide the data into two sectors: valid and invalid segments. Here is the test result:

  1. Invalid segment: Below 14 years
  2. Valid segment: 14-60 years
  3. Invalid segment: Above 60 years

In the above format, a valid segment refers to the value that the software accepts. This is called Valid Equivalence Partition.

Invalid Segments are values that are rejected by the software. It is referred to as Invalid Equivalence Partition.


Since we realise how useful is equivalence partition testing is, we need to understand their shortcomings also. The success of equivalence of partition is dependent on our ability to segment the data and make a partition. During testing the gym form above, we do not know the code embedded by the developer.

Let us consider that the developer coded: If age >14 and <60

<Allow user to submit the form>

Here the requirement shows that the age should be less than 14 or more than 14. Hence, with this test, we miss out on testing 14 as a value. As a tester, you need to be aware that equivalence partition testing shows that it doesn’t test all the combinations.


In short, this test largely depends on your ability to develop partitions. This test requires you to divide the data into invalid and valid inputs. To ensure that this testing is useful and effective, follow the best practices for maximum coverage and reduced testing time.

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