Testing Techniques

Equivalence Class Partitioning

Learning Outcome

3

Design test cases using ECP

2

Identify valid and invalid equivalence classes

1

Understand Equivalence Class Partitioning

Recall

Black box testing focuses on input and output

Equivalence Class Partitioning is one black box technique

In previous topic, we studied Black Box Testing

 Why Black Box Techniques?

Source code knowledge is not required

Used during system and acceptance testing

Focuses on user requirements

Easy to apply in manual testing

 Introduction to ECP

It divides input data into groups

Equivalence Class Partitioning is a Black Box Testing technique

Each group is treated as equivalent

Output

Input

Valid Equivalence class

Types of Equivalence Classes

Invalid Equivalence class

An equivalence class is a set of input values

One test case represents the entire class

System behaves the same for all values in the class

What is

Equivalence Class?

Valid Equivalence Class

  • Contains correct and acceptable input values

  • System should accept these values

  • Produces expected output

Invalid Equivalence Class

  • Contains incorrect or unacceptable input values

  • System should reject these values

  • Error message should be displayed

Steps to Apply ECP

Identify Conditions

Create Partitions

Define Test Cases

Identify Functions

Execute & Analyze

Run tests and evaluate results

Create one test per partition

Divide into valid and invalid classes

Define all input parameters and constraints

Determine which features need testing

1

2

3

4

4

4

5

Example

Condition:
Age must be between 18 and 60

Less than 18

18 to 60

Greater than 60

Valid Class

Invalid Class

Invalid Class

Test Case 1

Test Case 2

Test Case 3

Test Case Design Using ECP

Age = 15 → Rejected

Age = 65 → Rejected

 Age = 25 → Accepted

Risks Without Equivalence Partitioning

1. Time Waste

2-5x longer test execution times

2. Higher Costs

Increased maintenance for bloated test suites

3. Missed Defects

Critical boundary issues often overlooked

4. Resource Drain

Thousands of redundant test cases

Advantages and Limitations of ECP

  • Reduces number of test cases
  • Easy to use in manual testing
  • Better coverage, less effort

  • Not suitable for complex logic

  • Often used with Boundary Value Analysis

Advantages

Limitations

  • Boundary values may be missed

Summary

3

Ensures good coverage with fewer test cases

2

Helps in efficient manual testing

1

ECP is an important black box testing technique

Quiz

The main purpose of Equivalence Class Partitioning is to:

A. Increase number of test cases

B. Reduce test execution time

C. Reduce number of test cases

D. Test internal code

Quiz

The main purpose of Equivalence Class Partitioning is to:

A. Increase number of test cases

B. Reduce test execution time

C. Reduce number of test cases

D. Test internal code