Boundary Value Analysis (BVA) is a widely used software testing technique where test cases are designed to include boundary values. This technique is based on the observation that errors often occur at the boundaries of input values rather than within the range of valid input values. By focusing on the edges of input ranges, BVA helps ensure the robustness of the software by catching potential edge-case errors.
Scenario
Imagine a scenario where an online retail system offers discounts based on the total purchase amount. The discount rules are as follows:
- No discount for purchases below $50.
- 5% discount for purchases between $50 and $100.
- 10% discount for purchases between $101 and $200.
- 15% discount for purchases above $200.
Using Boundary Value Analysis, we can identify the critical boundaries for this discount system:
- $49 (just below the first boundary)
- $50 (exactly at the first boundary)
- $51 (just above the first boundary)
- $100 (exactly at the second boundary)
- $101 (just above the second boundary)
- $200 (exactly at the third boundary)
- $201 (just above the third boundary)
Sample Test Cases
1. Test Case 1: Below the First Boundary
- Input: Total Purchase Amount = $49
- Expected Output: No discount
2. Test Case 2: At the First Boundary
- Input: Total Purchase Amount = $50
- Expected Output: 5% discount
3. Test Case 3: Just Above the First Boundary
- Input: Total Purchase Amount = $51
- Expected Output: 5% discount
4. Test Case 4: At the Second Boundary
- Input: Total Purchase Amount = $100
- Expected Output: 5% discount
5. Test Case 5: Just Above the Second Boundary
- Input: Total Purchase Amount = $101
- Expected Output: 10% discount
6. Test Case 6: At the Third Boundary
- Input: Total Purchase Amount = $200
- Expected Output: 10% discount
7. Test Case 7: Just Above the Third Boundary
- Input: Total Purchase Amount = $201
- Expected Output: 15% discount
Explanation of Test Cases
- Test Case 1: Verifies that the system correctly applies no discount just below the first threshold.
- Test Cases 2 and 3: Check the system’s behavior exactly at and just above the first discount threshold.
- Test Cases 4 and 5: Ensure that the 5% discount is correctly applied up to and just beyond the $100 mark.
- Test Cases 6 and 7: Verify that the 10% discount is applied correctly up to $200 and the 15% discount for any amount above $200.
By testing these boundaries, we ensure that the system behaves correctly at critical points where errors are most likely to occur. BVA helps catch off-by-one errors, incorrect conditional statements, and other issues that can arise at the edges of input ranges.
Benefits of Boundary Value Analysis
- Efficiency: Reduces the number of test cases needed to cover all possible input ranges by focusing on boundaries.
- Effectiveness: Increases the likelihood of detecting defects that occur at boundary conditions.
- Simplicity: Easy to understand and implement, making it suitable for various testing scenarios.
Boundary Value Analysis is a powerful technique that helps testers ensure that the software handles edge cases correctly, ultimately leading to more robust and reliable applications.
