docs: add manual testing guide for slash command validation

[mnriem]

Adds a top-level TESTING.md that describes the manual test process PR submitters must follow when their changes affect slash commands.

What's included

• Process overview — identify affected commands → setup test project → run commands → report results
• Local setup — editable install via uv pip install -e . + specify init --offline
• Reporting template — copy-paste block for PR submissions with agent/OS/shell metadata
• Agent prompt for test selection — PR submitters paste this into their agent, which analyzes git diff --name-only main and maps changed files to affected commands using:
  • Direct command template mapping
  • Transitive script dependencies (e.g., common.sh → create-new-feature.sh → /speckit.specify)
  • Extension hook resolution (e.g., extension.yml before_specify hook → /speckit.specify)
  • Template consumption tracking
  • Prerequisite chain resolution

The agent's reasoning output (which files affect which commands, and why) is submitted alongside the test results in the PR.

Why

There was no documented process for validating that slash commands actually work after code changes. Automated tests cover file generation, placeholder replacement, and script execution — but nobody was verifying the full agent-mediated command invocation path. This fills that gap with a lightweight manual process.

[Copilot]

Pull request overview

Adds a new top-level manual testing guide to ensure PRs that impact /speckit.* slash commands include end-to-end, agent-mediated validation steps and a standard reporting format.

Changes:

• Add TESTING.md describing a manual test workflow for slash command changes.
• Provide a copy/paste PR reporting template for manual test results.
• Include an “agent prompt” to map changed files to affected commands and prerequisite test ordering.

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[mnriem]

@copilot open a new pull request to apply changes based on the comments in this thread

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.

Comments suppressed due to low confidence (1)

TESTING.md:22

• /tmp/speckit-test is POSIX-specific and won’t work on Windows (and may be undesirable in some environments). Consider using a placeholder like <test-project-dir> (or showing both a Unix and Windows example), or recommending specify init --here in an empty directory to keep the instructions cross-platform.

# Initialize a test project using your local changes
specify init /tmp/speckit-test --ai <agent> --offline
cd /tmp/speckit-test

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

TESTING.md:20

• The Windows activation hint looks incorrect/incomplete: standard venv activation scripts are .venv\Scripts\Activate.ps1 (PowerShell) or .venv\Scripts\activate.bat (cmd), whereas .venv\Scripts\activate usually won’t exist. This repo’s docs/local-development.md uses the Activate.ps1 form—please align this guide so Windows users can follow it verbatim.

source .venv/bin/activate  # On Windows: .venv\Scripts\activate
uv pip install -e .

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