Rewrite docs/Testing.md as a focused testing guide

[AndyTWF]

Why

The old docs/Testing.md was 400 lines of unfocused guidance — heavy on running commands and debugging env vars, light on what to test and when. It didn't answer the key questions a contributor needs:

• What kind of test should I write for this change?
• What does a good PR test suite look like?
• When is E2E worth the cost vs unit?

The "integration" layer was also misleading — it's 4 files all testing interactive mode subprocess behavior, not a general-purpose middle tier.

What changed

• Replaced the 400-line emoji-heavy Testing.md with a 249-line opinionated guide that answers "I wrote a new command — what tests do I need?"
• Defined four test layers (unit, E2E, TTY, subprocess) with clear purpose and when-to-use guidance
• Made unit and E2E tests mandatory for every command
• Added decision tree + explicit rules for choosing the right test layer
• Honestly described test/integration/ as 4 interactive-mode files, not a general-purpose tier
• Added helpers reference tables (core helpers, mock SDKs, factories, NDJSON, TTY)
• Moved test structure/describe blocks/running tests out of AGENTS.md into Testing.md with a cross-reference

Test plan

• Docs-only change — no code modified
• pnpm exec eslint . passes (0 errors)
• Read Testing.md end-to-end and confirm it answers the key contributor question
• Verify AGENTS.md cross-reference link resolves correctly

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
cli-web-cli	Ready	Preview, Comment	Mar 30, 2026 9:12am

[claude-code-ably-assistant]

Walkthrough

This PR rewrites docs/Testing.md from a 400-line emoji-heavy document into a concise 249-line opinionated guide focused on answering the key contributor question: "I wrote a new command — what tests do I need?" Alongside this, 24 lines of test guidance are removed from AGENTS.md and replaced with a single cross-reference link to the new doc, consolidating all testing documentation in one place.

Changes

Area	Files	Summary
Docs	docs/Testing.md	Full rewrite: adds test layer decision table, decision tree, mandatory/optional test rules, running tests table, and helpers reference; removes decorative HTML, collapsed sections, and misleading integration tier description
Config	AGENTS.md	Removes 24 lines of duplicated test structure/describe block/running-tests content; replaces with a single cross-reference link to docs/Testing.md

Review Notes

• Docs-only change — no source code or tests modified; no functional behavior affected.
• AGENTS.md is the authoritative agent instruction file — removing content from it and pointing to an external doc means agents/LLMs must now follow the link to get describe-block rules and running-test commands. Verify the cross-reference link resolves correctly from AGENTS.md's location.
• "integration" layer reframing — the doc now explicitly states test/integration/ is not a general-purpose tier (just 4 interactive-mode files) and hints at a future rename. This is accurate but worth confirming as a team consensus before it lands.
• Required describe blocks rule moved out of AGENTS.md — this is a mandatory convention enforced in code review. Confirm reviewers are comfortable with it living only in Testing.md going forward.