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 skills add xonovex/platform --skill testing-guidegit clone --depth 1 https://github.com/xonovex/platformWrote 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/xonovex/platform/testing-guide)<a href="https://agentmods.dev/skills/xonovex/platform/testing-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/testing-guide/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/xonovex/platform/testing-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/testing-guide.svg" alt="Reviewed on agentmods" width="80" 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 5.1 | $0.00130 | $0.01121 |
| Opus 5.5 | $0.00052 | $0.00448 |
| Sonnet 5.5 | $0.00026 | $0.00224 |
| Haiku 4.5 | $0.00013 | $0.00112 |
Grade A, and why
testing-guide 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 1mo 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 — 54 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Writing a Single Good Test
How to structure, name, populate, and verify one test, and how to pick the right test double: independent of any framework. It governs the shape of an individual test, not the rhythm in which you write tests.
Essentials
- Structure every test as Arrange-Act-Assert - set up, run one action, verify the outcome, see references/test-structure-and-first.md
- Make each test meet FIRST - Fast, Independent, Repeatable, Self-validating, Timely, see references/test-structure-and-first.md
- Name the right double for the job - Dummy / Stub / Spy / Mock / Fake are distinct, not synonyms, see references/test-double-taxonomy.md
- Prefer state verification; mock only true outputs - assert outcomes, reserve call-checking for external commands, see references/state-vs-behaviour-and-what-to-mock.md
- Mock at architectural seams, not internals - double the payment gateway, never value objects or the system under test, see references/state-vs-behaviour-and-what-to-mock.md
- Read a failing test as a smell report - fragile, obscure, eager, erratic tests each name a fix, see references/test-smells-and-fixtures.md
Gotchas
- "Mock" is not a synonym for "test double". A Mock holds pre-programmed call expectations and is verified; most things people call mocks are actually Stubs that answer queries with canned state.
- A Stub answers queries (state); a Mock verifies commands (behaviour). Asserting on calls when state would do couples the test to the implementation and makes it Fragile.
- AAA is three phases, not four. Explicit Teardown belongs to the Four-Phase Test and is usually unnecessary for a true unit test.
- A Spy is not a Mock: a Spy passively records calls for the test to assert later; a Mock owns the expectations itself and fails on an unexpected or missing call.
- A Fake is not a Stub: a Fake has a real, working, shortcut implementation (an in-memory store); a Stub only returns hard-coded answers with no logic.
- A test that needs many doubles or asserts on internal calls is a coupling signal: fix the production design, and take the coupling diagnosis to connascence-guide, not a bigger fixture.
- FIRST's "I" (Independent / Isolated) and "S" (Self-validating / Self-verifying) both circulate; same intent, neither spelling is wrong.
What ships with it
8 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.
- 1mo ago First seen · 54 lines · 130 tokens per session scan A 401bb8218171
testing-guide is a skill published in the GitHub repository xonovex/platform (6 stars, last pushed 4d ago), licensed MIT. It adds 130 tokens to every session and 1,121 once invoked, about $0.0005 per session on Opus 5.5. 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 2026-09-08.
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