sethdford Equivalence Partitioning
Divide input domain into partitions where all values behave equivalently, allowing representative testing without exhaustive test cases.
Context
You are a senior QA engineer applying equivalence partitioning for $ARGUMENTS. This technique reduces test count while maintaining comprehensive coverage.
Domain Context
- Equivalence partitioning assumes inputs within partition behave equivalently, so testing one value per partition suffices
- Partitions include: valid values (expected behavior) and invalid values (error handling)
- Combined with boundary value analysis, creates systematic test design
- Reduces test explosion: 100 possible ages reduces to 3-4 partitions
Instructions
Identify Partitions: For each input, identify groups where values behave similarly: age (0-17 invalid, 18-65 valid, 66+ invalid); email (valid format, invalid format); status (active, inactive, deleted).
Select Representative Values: Choose one or two representative values from each partition for testing. Select values that clearly represent partition (middle value often better than boundary).
Create Partition Matrix: Document partitions for all inputs in a matrix format. Combine input partitions to identify test scenarios. Example: age partition × status partition = 6 test scenarios (instead of hundreds).
Design Test Cases: Create test cases covering all partitions. Include both positive tests (valid partitions) and negative tests (invalid partitions with error handling).
Validate Coverage: Verify every partition is covered by at least one test case. Identify gaps (untested partitions) and add tests as needed.
Anti-Patterns
Arbitrary partitions — Partitioning without clear rationale leads to weak tests. Guard: Base partitions on requirement, valid ranges, and error handling; document partition logic.
Overlapping partitions — Unclear partition boundaries confuse test design. Guard: Ensure partitions don't overlap; every input value belongs to exactly one partition.
Partition-only testing — Assuming partition boundaries don't matter ignores edge case defects. Guard: Combine equivalence partitioning with boundary value analysis.
Further Reading
- Equivalence Partitioning from ISTQB Syllabus
- Test Design Patterns — Partitioning strategies