Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/djscheuf/agentic-dev-ecosystem-template/design-test-casesnpx skills add djscheuf/agentic-dev-ecosystem-template --skill design-test-casesgit clone --depth 1 https://github.com/djscheuf/agentic-dev-ecosystem-templateWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/djscheuf/agentic-dev-ecosystem-template/design-test-cases)<a href="https://agentmods.dev/skills/djscheuf/agentic-dev-ecosystem-template/design-test-cases"><img src="https://agentmods.dev/badge/skills/djscheuf/agentic-dev-ecosystem-template/design-test-cases.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00025 | $0.00648 |
| Opus 5 | $0.00013 | $0.00324 |
| Sonnet 5 | $0.00005 | $0.00130 |
| Haiku 4.5 | $0.00003 | $0.00065 |
Grade A, and why
design-test-cases scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 101 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Design Test Cases
Purpose
Analyze requirements and design test cases before writing any code. This is the planning phase of TDD.
Trigger
- Starting a new feature or bug fix
- Before writing any production code
- When clarifying approach to an Implementation Plan
Inputs Required
- Implementation Plan
- Acceptance criteria (if available)
- Relevant domain context
Workflow Steps
Step 1: Understand the Requirement
Analyze the requirements and answer:
1. What is the core behavior being requested?
2. What are the inputs and expected outputs?
3. What are the boundary conditions?
4. What could go wrong (error cases)?
Step 2: Review Existing Test Cases
Step 3: Identify All Test Cases
Create a test case list covering:
HAPPY PATH:
- [ ] Basic successful scenario
- [ ] Typical use case with valid inputs
EDGE CASES:
- [ ] Empty/null inputs
- [ ] Minimum valid values
- [ ] Maximum valid values
- [ ] Boundary conditions
ERROR CASES:
- [ ] Invalid input types
- [ ] Out of range values
- [ ] Missing required data
- [ ] System/dependency failures
SPECIAL CASES:
- [ ] Concurrent access (if applicable)
- [ ] Idempotency requirements
- [ ] Performance constraints
Utilize documented cases, and fill in any gaps.
Step 3: Prioritize Test Cases
Order tests by:
1. Core happy path (proves basic functionality)
2. Critical error handling
3. Edge cases
4. Nice-to-have scenarios
Step 4: Design Test Structure
For each prioritized test, define:
- Test name following convention: Method_Scenario_ExpectedResult
- Arrange: What setup is needed?
- Act: What action triggers the behavior?
- Assert: What outcome proves success?
Step 5. Output Test Cases
Capture test cases in a JSON file that follows the schema in schema/test-cases.schema.json. File should be named {workstream}.test-cases.json and placed in the same directory as the implementation plan.
Output the test cases in the following format:
- Test name following convention: Method_Scenario_ExpectedResult
- Arrange: What setup is needed?
- Act: What action triggers the behavior?
- Assert: What outcome proves success?
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 5d ago First seen · 101 lines · 25 tokens per session scan A 3d0e7779f72c
design-test-cases is a skill published in the GitHub repository djscheuf/agentic-dev-ecosystem-template (12 stars, last pushed yesterday), licensed MIT. It adds 25 tokens to every session and 648 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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