A wholesaler sells printer cartridges. The minimum order quantity is 5. There is a 20% discount for orders of 100 or more printer cartridges. You have been asked to prepare test cases using various…

Question

Options

• A5, 6, 20
• B4, 5, 80.
• C4, 5, 99.
• D1, 20, 100.

• A
  5% (2)
• B
  14% (6)
• C
  75% (33)
• D
  7% (3)

Explanation

Option C is correct because 4, 5, and 99 are all genuine boundary values: 4 is just below the minimum order threshold (invalid), 5 is exactly at the minimum (the lower boundary itself), and 99 is just below the discount threshold of 100 - making all three values sit at or immediately adjacent to a partition boundary.

Why the distractors fail:

• A (5, 6, 20): 20 sits deep inside the valid/no-discount partition - it's an equivalence class representative, not a boundary value.
• B (4, 5, 80): 80 is similarly stranded in the middle of a partition with no boundary significance.
• D (1, 20, 100): 100 is a valid boundary, but 1 is two steps away from the actual boundary at 4/5, and 20 is again a mid-partition value.

Memory tip: BVA lives at the edges, not the middle. For each boundary, think in triplets - (boundary − 1), (boundary), (boundary + 1). Here the two boundaries are 5 (minimum order) and 100 (discount threshold), giving you candidate values of 4, 5, 6 and 99, 100, 101. Any answer containing a "comfortable middle" value like 20 or 80 is mixing BVA with Equivalence Partitioning.

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