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/dean0x/devflow/testingnpx skills add dean0x/devflow --skill testinggit clone --depth 1 https://github.com/dean0x/devflowWhat 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 | $0.00070 | $0.01265 |
| Opus 5 | $0.00035 | $0.00633 |
| Sonnet 5 | $0.00014 | $0.00253 |
| Haiku 4.5 | $0.00007 | $0.00127 |
Grade A, and why
testing 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 — 140 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Testing Patterns
Iron Law
TESTS VALIDATE BEHAVIOR, NOT IMPLEMENTATION [4][8]
A test should fail when behavior breaks, not when implementation changes. Mock at boundaries, not internals. Test the contract, not the code path. If tests are hard to write, the design is wrong — fix the architecture, not the tests. [3][8]
Testing Shapes [6][7][10]
| Shape | Guidance |
|---|---|
| Pyramid [6] | Many unit → fewer integration → fewest E2E |
| Trophy [7] | Integration tests give best ROI for UI-heavy code |
| Google [4] | 70% unit / 20% integration / 10% E2E; avoid E2E excess [12] |
Test Doubles Taxonomy [1][9]
| Type | When to Use | Example |
|---|---|---|
| Dummy | Fill unused parameters | null, empty object |
| Stub | Return canned data, no assertions | getRate: () => 0.1 |
| Spy | Record calls, assert after | jest.spyOn() on public methods |
| Mock | Pre-programmed expectations | expect(fn).toHaveBeenCalledWith(x) |
| Fake | Working substitute (in-memory DB) | InMemoryUserRepo |
"Mock roles, not objects" — mock interfaces you own, never third-party internals [3][9].
Test Design Red Flags
| Red Flag | Symptom | Root Cause | Fix |
|---|---|---|---|
| Complex setup >10 lines [8] | beforeEach with 6+ mocks |
Too many dependencies | Split service; use fakes [1][4] |
| Repetitive try/catch [8] | Same pattern >3 times | API throws, not Result | Migrate to Result types [4] |
| Nested mock structures [1][3] | mockDb.orders.create: jest.fn() |
Tight coupling | Extract interface; use fake [9] |
| Spying on private methods [8] | jest.spyOn(obj as any, '_method') |
Tests implementation | Assert observable output [4] |
// VIOLATION: Tests private implementation [8]
jest.spyOn(cart as any, 'updateTotal');
expect(spy).toHaveBeenCalled(); // Tests HOW
// CORRECT: Tests observable behavior [4]
cart.addItem({ id: '1', price: 10 });
expect(cart.getTotal()).toBe(10); // Tests WHAT
What ships with it
5 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.
- 2d ago First seen · 140 lines · 70 tokens per session scan A c1c08e2fe3cd
testing is a skill published in the GitHub repository dean0x/devflow (19 stars, last pushed 2d ago), licensed MIT. It adds 70 tokens to every session and 1,265 once invoked, about $0.0003 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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