Verify Interactive CLI

Verify vp's interactive CLI prompts

The PTY snapshot suite covers scripted prompt flows. This skill complements it by driving an installed CLI in tmux, capturing clean output, and checking a prompt over several seconds for a spinner animating underneath it (a real, recurring UX bug class, e.g. the "Preparing migration" and "Checking Node.js version support" spinners).

Prerequisites

• tmux (macOS has none by default): brew install tmux.
• The global vp must contain the code under test. To exercise working-tree changes, rebuild first: pnpm bootstrap-cli (~5 min), then confirm with vp --version.

Driver

interactive-cli-tmux-driver.sh is bundled in this skill's directory.

# Run to completion, auto-accepting every prompt's DEFAULT; prints a clean transcript.
.claude/skills/verify-interactive-cli/interactive-cli-tmux-driver.sh <project-dir> "vp migrate"

# STOP at a specific prompt (do NOT answer it) and check for a spinner animating under it.
.claude/skills/verify-interactive-cli/interactive-cli-tmux-driver.sh <project-dir> "vp migrate" "Upgrade Node.js"

How it works:

• Runs the command in a detached tmux session; tmux capture-pane -p yields clean text (clack's in-place redraws overwrite, so only resolved lines remain), far cleaner than expect's raw ANSI capture.
• Auto-accepts each prompt's default by sending Enter when the pane goes STABLE. A waiting prompt is static; animating spinners keep the pane changing, so Enter never fires mid-work.
• End-detection uses ; echo "$M1$M2 exit=$?" where M1/M2 are split vars, so the literal end marker is not in the typed command line (otherwise a grep matches the echoed command, not the program output).
• With a STOP_AT regex it halts at the target prompt and captures twice ~3s apart: identical captures = static prompt (OK); differing captures (or a Checking ... (Xs) line) = a spinner is animating under the prompt = a UX bug.

Setting up a target project

Create a throwaway project that triggers the prompts you want to see, e.g. a fresh Vite app whose .node-version is below the supported range to exercise the Node-upgrade confirm:

mkdir -p /tmp/vp-demo && cd /tmp/vp-demo
printf '{\n  "name":"d","private":true,"type":"module","packageManager":"pnpm@10.18.0",\n  "scripts":{"build":"vite build","test":"vitest run"},\n  "devDependencies":{"vite":"^8.0.0","vitest":"^4.1.0"}\n}\n' > package.json
echo "24.3.0" > .node-version
printf 'import { defineConfig } from "vite";\nexport default defineConfig({});\n' > vite.config.ts
git init -q && git add -A && git -c user.email=x@x -c user.name=x commit -qm init

When you find a spinner-over-prompt bug

Fix it test-first: the prompt's code must pause the migration progress spinner before the confirm renders. Assert the call order is ['pause', 'confirm']. Reference fix: upgradeUnsupportedNodeVersions (in packages/cli/src/migration/migrator/setup.ts) takes a pauseProgress callback that bin.ts wires to clearMigrationProgress, called right before prompts.confirm.

Gotchas

• clack's active-prompt marker here is › (not always ◆); detect a waiting prompt by pane stability, not a specific glyph.
• VP_SKIP_INSTALL=1 skips the dependency install but breaks steps that load vite.config.ts (e.g. the prettier auto-migration) because vite isn't installed; use it only when you stop before the install step.
• A & inside a background task detaches the script, so the task reports "completed" early while it keeps running; poll a status file or capture-pane to track real progress.