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Equivalence Partitioning

Equivalence Partitioning (EP) is a test case design technique where input data is divided into logical groups (partitions) such that all values in a partition are expected to behave the same way.

EP answers: “Which inputs can be treated as equivalent?”

1. Definition

Equivalence Partitioning (EP) is a test case design technique where input data is divided into logical groups (partitions) such that all values in a partition are expected to behave the same way.

EP answers: “Which inputs can be treated as equivalent?”

2. Purpose of Equivalence Partitioning

  • Reduce the number of test cases
  • Improve test coverage
  • Avoid redundant testing
  • Identify valid and invalid input groups

3. Types of Equivalence Partitions

  • Valid Equivalence Partition
  • Invalid Equivalence Partition

Each partition is tested using one representative value.

4. How to Apply Equivalence Partitioning (Steps)

  1. Identify input conditions
  2. Divide inputs into valid and invalid partitions
  3. Select one value from each partition
  4. Create test cases using those values

5. Real-Time Example

Age field requirement: Age must be between 18 and 60.

  • Valid partition: 18–60
  • Invalid partition 1: < 18
  • Invalid partition 2: > 60

Test values:

  • 30 (valid)
  • 15 (invalid)
  • 65 (invalid)

6. Equivalence Partitioning vs Exhaustive Testing

Aspect EP Exhaustive Testing
Test cases Few Many
Efficiency High Low
Coverage Logical Complete (impossible)

7. When to Use Equivalence Partitioning

  • Input fields with ranges
  • Forms with validations
  • Numeric, text, or dropdown inputs

8. Common Mistakes

  • Treating boundary values as normal EP values
  • Missing invalid partitions
  • Assuming one valid case is always enough

9. Interview-Ready Answers

Short answer:

Equivalence partitioning divides input data into groups where one value represents the entire group.

Detailed answer:

Equivalence partitioning reduces test cases by grouping inputs that are expected to produce the same outcome and testing one value from each group.

10. Key Takeaway

Equivalence Partitioning helps testers test smarter by reducing redundancy without losing coverage.