Pairwise / Combinatorial Testing
Pairwise Testing (also called Combinatorial Testing) is a test case design technique where test cases are designed to cover all possible pairs of input parameter values, instead of testing every possible combination.
Pairwise testing answers: “Can we reduce combinations while still covering interactions effectively?”
1. Definition
Pairwise Testing (also called Combinatorial Testing) is a test case design technique where test cases are designed to cover all possible pairs of input parameter values, instead of testing every possible combination.
Pairwise testing answers: “Can we reduce combinations while still covering interactions effectively?”
2. Why Pairwise Testing Is Needed
- Exhaustive testing of combinations is impossible
- Defects often occur due to interaction between two parameters
- Pairwise testing reduces test cases dramatically while maintaining coverage
3. Concept Behind Pairwise Testing
- Most defects are caused by interaction of two factors, not all factors
- Testing all possible pairs gives high confidence with fewer test cases
4. When to Use Pairwise / Combinatorial Testing
- Multiple input fields or parameters
- Configuration-based systems
- Forms with many dropdowns or options
- Environment combinations (browser, OS, role, language)
5. Real-Time Example
Login Form Parameters
- Browser: Chrome, Firefox
- OS: Windows, macOS
- User Role: Admin, User
Total combinations: 2 × 2 × 2 = 8
Pairwise testing may reduce this to: 4 test cases while still covering all pairs.
6. Pairwise Testing vs Exhaustive Testing
| Aspect | Pairwise Testing | Exhaustive Testing |
|---|---|---|
| Test cases | Few | Very many |
| Coverage | All pairs | All combinations |
| Efficiency | High | Low |
| Practicality | Yes | No |
7. Manual Tester’s Role
- Identify parameters and values
- Determine critical combinations
- Apply pairwise logic manually (or conceptually)
- Validate interaction defects
8. Benefits of Pairwise Testing
- Significant reduction in test cases
- Better coverage than random testing
- Efficient for time-constrained projects
- Ideal for configuration testing
9. Common Defects Found
- Configuration conflicts
- Environment-specific issues
- Feature interaction failures
10. Common Mistakes
- Using pairwise when parameters are dependent
- Missing critical business combinations
- Blindly trusting reduced test sets
11. Interview-Ready Answers
Short answer:
Pairwise testing is a technique where test cases are designed to cover all possible pairs of input parameters.
Detailed answer:
Pairwise or combinatorial testing reduces the number of test cases by ensuring that every pair of input values is tested at least once, effectively detecting interaction defects.
12. Key Takeaway
Pairwise Testing delivers maximum coverage with minimal effort, making it highly effective for complex input combinations.