Equivalence Class Partitioning

Equivalence Class Partitioning

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While testing any kind of application, it is nearly impossible or really very time-consuming to test all the sets of input combinations. So, in order to efficiently test an application, we use software testing techniques like – equivalence class partitioning.

Using this technique, we can test software applications effectively with a limited set of test data. So, let’s check this technique in detail now.

What is Equivalence Class Partitioning?

Equivalence class partitioning is a black-box testing technique or specification-based testing technique in which we group the input data into logical partitions called equivalence classes.

All the data items lying in an equivalence class are assumed to be processed in the same way by the software application to be tested when passed as input.

So, instead of testing all the combinations of input test data, we can pick and pass any of the test data from a particular equivalence class to the application and assume that the application will behave in the same way for the other test data of that class. Let’s understand this with the help of an example.


Consider an example of an application that accepts a numeric number as input with a value between 10 to 100 and finds its square. Now, using equivalence class testing, we can create the following equivalence classes-

Equivalence ClassExplanation
Numbers 10 to 100This class will include test data for a positive scenario.
Numbers 0 to 9This class will include test data that is restricted by the application. Since it is designed to work with numbers 10 to 100 only.
Greater than 100This class will again include test data that is restricted by the application but this time to test the upper limit.
Negative numbersSince negative numbers can be treated in a different way so, we will create a different class for negative numbers in order to check the robustness of the application.
AlphabetsThis class will be used to test the robustness of the application with non-numeric characters.
Special charactersJust like the equivalence class for alphabets, we can have a separate equivalence class for special characters.

Identification of Equivalence Classes

Let’s discuss some points or best practices regarding the identification of Equivalence classes-

  • Cover all test data types for positive and negative test scenarios. We have to create test data classes in such a way that covers all sets of test scenarios but at the same time, there should not be any kind of redundancy.
  • If there is a possibility that the test data in a particular class can be treated differently then it is better to split that equivalence class.

    For example, in the above example, the application doesn’t work with numbers – less than 10. So, instead of creating 1 class for numbers less than 10, we created two classes – numbers 0-9 and negative numbers. This is because there is a possibility that the application may handle negative numbers differently.

Also check – Boundary Value Analysis

Advantages of Equivalence Classes Testing

  • With the help of equivalence class testing, the number of test cases greatly reduces maintaining the same test coverage.
  • This testing technique helps in delivering a quality product within a minimal time period.
  • It is perfectly suitable for software projects with time and resource constraints.
  • It improves the quality of testing as the software testers have to work with a smaller dataset of test data, thus focusing more on quality.

Disadvantages of Equivalence Classes Testing

  • The whole success of equivalence class testing relies on the identification of equivalence classes. The identification of these classes relies on the ability of the testers who creates these classes and the test cases based on them.
  • In the case of complex applications, it is very difficult to identify all sets of equivalence classes and requires a great deal of expertise from the tester’s side.
  • Incorrectly identified equivalence classes can lead to lesser test coverage and the possibility of defect leakage.

With this, we have come to the end of our tutorial on equivalence class partitioning. If you have any questions, please ask in the comment section. Also, check out our complete software testing tutorial series below.

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