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/plainlang/plain-forge/add-acceptance-testnpx skills add plainlang/plain-forge --skill add-acceptance-testgit clone --depth 1 https://github.com/plainlang/plain-forgeWhat 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 | $0.00048 | $0.00995 |
| Opus 5 | $0.00024 | $0.00498 |
| Sonnet 5 | $0.00010 | $0.00199 |
| Haiku 4.5 | $0.00005 | $0.00100 |
Grade A, and why
add-acceptance-test 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 2d 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 — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Add Acceptance Test
Always use the skill load-plain-reference to retrieve the ***plain syntax rules — but only if you haven't done so yet.
Workflow
- Identify the target
.plainfile and the functional spec to attach the acceptance test to. If ambiguous, ask the user. - Read the file to understand the functional spec, existing acceptance tests (if any), and the
***test reqs***section (acceptance tests are implemented according to test reqs). - Draft the acceptance test(s) following the rules below.
- Nest them under the target functional spec using a
***acceptance tests***subsection. - Read the file again to confirm correct placement, indentation, and syntax.
When to Add Acceptance Tests
- The functional spec's correct behavior is non-obvious or easily misinterpreted.
- The spec involves edge cases, boundary conditions, or specific numeric outcomes.
- The user explicitly requests verification criteria.
- The spec was added via the
add-functional-specskill and warrants testable success criteria.
Format
Acceptance tests are nested under the functional spec they verify, using a ***acceptance tests*** subsection:
***functional specs***
- :Task: items are processed in batches of 100.
***acceptance tests***
- Processing 250 :Task: items should result in 3 batches.
- Each batch should contain at most 100 items.
Key formatting rules:
- The
***acceptance tests***header is indented under the functional spec it belongs to. - Each test bullet is indented under the
***acceptance tests***header. - Multiple acceptance tests can be listed under a single functional spec.
Rules
Conformance with the Functional Spec
An acceptance test is essentially an example that illustrates the functional spec — it clarifies intent by showing a concrete scenario. It may imply minor code changes, but those should not be substantial. The acceptance test must be consistent with the functional spec it is nested under. If the acceptance test asserts behavior that contradicts, narrows, or extends the functional spec in ways not implied by it, the system will reject it as a conflicting acceptance test. Before writing, re-read the parent functional spec and ensure every assertion in the acceptance test is a direct, logical consequence of what the spec states.
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.
- 2d ago First seen · 102 lines · 48 tokens per session scan A e349d7e23ca4
add-acceptance-test is a skill published in the GitHub repository plainlang/plain-forge (55 stars, last pushed 5d ago), licensed MIT. It adds 48 tokens to every session and 995 once invoked, about $0.0002 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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