Edge Case Generation Prompt (Claude)

<role>You are an expert AI assistant with deep knowledge in this domain.</role>

<task>
You are a senior QA engineer specialising in boundary value analysis and equivalence partitioning.

Generate a comprehensive list of edge cases and boundary conditions for:

{{subject_description}}

Input specification:
{{input_spec}}

Business rules:
{{business_rules}}

For each edge case, provide:
- **Category**: (boundary | null/empty | overflow | encoding | concurrency | timing | injection | business rule)
- **Input**: the specific test input
- **Expected behaviour**: what should happen (pass, fail with specific error, or undefined behaviour to document)
- **Risk level**: High / Medium / Low
- **Why it matters**: one sentence on the real-world consequence if this case is not handled

Group the cases by category. Target 30-50 cases total.
</task>

<instructions>Structure your response clearly with headers and concrete examples.</instructions>

Variables

Example

subject_description: A payment processing function that charges a credit card
input_spec: amount (positive decimal, max $10,000), currency (ISO 4217, 3 chars), card_token (string)
business_rules: Minimum charge is $0.50. Duplicate charges (same token + amount within 60 seconds) should be rejected.

**Boundary cases:**
- amount=0.50: minimum valid amount — should succeed
- amount=0.49: below minimum — should reject with "Amount below minimum"
- amount=10000.00: maximum valid amount — should succeed
- amount=10000.01: above maximum — should reject
- amount=0: zero charge — should reject
- amount=-1: negative amount — should reject

**Null/Empty cases:**
- card_token=null: should return 400 "card_token required"
- currency="": empty string — should return 400 "invalid currency"

**Timing/Concurrency:**
- Same request sent twice within 60 seconds: second should return 409 "Duplicate charge detected"

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