Borrowing it
Nothing to install: this file belongs to shift-editor/shift. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/shift-editor/shift/main/.agents/skills/writing-e2e-tests/SKILL.mdgit clone --depth 1 https://github.com/shift-editor/shiftWrote 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/shift-editor/shift/writing-e2e-tests)<a href="https://agentmods.dev/skills/shift-editor/shift/writing-e2e-tests"><img src="https://agentmods.dev/badge/skills/shift-editor/shift/writing-e2e-tests/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/shift-editor/shift/writing-e2e-tests"><img src="https://agentmods.dev/badge/skills/shift-editor/shift/writing-e2e-tests.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 | $0.00096 | $0.02793 |
| Opus 5.5 | $0.00038 | $0.01117 |
| Sonnet 5.5 | $0.00019 | $0.00559 |
| Haiku 4.5 | $0.00010 | $0.00279 |
Grade A, and why
writing-e2e-tests 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 20d 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 — 144 lines — stays where its author put it; the contents beside it link to each section on GitHub.
/writing-e2e-tests — How desktop E2E tests are written
An E2E test is worth its cost only when it fails for exactly one reason: the user-visible behavior it names is broken. It must not fail because the machine was slow, the theme changed, a sidebar moved, or a retry happened to pass.
Read /writing-tests first for the general rules (observable state, no mocks, migration ledgers). Read apps/desktop/e2e/README.md for the full fixture and project reference. This skill is the checklist that turns those into a test that stays green for the right reasons.
Choose the layer before writing anything
| The behavior is… | Owning test |
|---|---|
| Pure computation (layout math, latch rules, range selection) | Pure unit test — extract the function first |
| Observable through editor state after a click, drag, or key | TestEditor tool or command test |
| A real browser or Electron contract (DOM events, focus, native menus, dialogs, windows, processes, files) | Semantic Playwright test |
| Appearance: colours, strokes, handles, layout | One focused golden, after a semantic precondition |
| Hardware rendering, GPU residency, WebGPU presentation | gpu project test |
| Save, quit, crash, recovery, file activation, cross-OS paths | platform project test |
If most assertions in a draft E2E test read editor state after page.evaluate, the behavior probably belongs in TestEditor. Keep the E2E test as a thin proof that the real UI reaches it.
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.
- 20d ago Changed · +1 lines 77a11d25c5c8
- 28d ago Changed · +6 lines 9e843b8af635
- 1mo ago First seen · 137 lines · 96 tokens per session scan A 0b20ef8b71a7
writing-e2e-tests is a skill published in the GitHub repository shift-editor/shift (379 stars, last pushed today), licensed Apache-2.0. It adds 96 tokens to every session and 2,793 once invoked, about $0.0004 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 2026-09-27.
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