refactor(studio): share the flat-inspector test render harness across panel suites

[vanceingalls]

Groundwork split out of the VST stack so it can be reviewed on its own — no VST code here.

The eight flat property-panel test suites each carried an identical copy of the React act-environment setup and a local renderInto() helper. Both move into testRenderUtils.tsx.

Net +54/-122. No behavior change: setupReactActEnvironment() registers the same document.body cleanup each file registered inline, and renderInto() is the same createRoot + act wrapper.

Base of the VST stack: #2920

🤖 Generated with Claude Code

[vanceingalls]

• feat(studio): VST FX panel section behind STUDIO_VST_ENABLED #2923
• feat(studio,core,player): stream VST-processed audio in the studio player #2922
• feat(engine,producer): apply VST chains in the offline audio mix #2921
• feat(studio-server,cli): VST sidecar host and carve API #2920
• refactor(studio): share the flat-inspector test render harness across panel suites #2919 👈 (View in Graphite)
• main

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[vanceingalls]

R1 — COMMENT

Author is vanceingalls; R1 stays a comment by convention regardless. CI green at head, zero prior reviews. Harness extraction is sound — 7 real consumers is well past the premature-abstraction bar, { host, root } matches every destructure, no production coupling.

Non-blockers

1. packages/studio/src/components/editor/propertyPanelFlatTextSection.test.tsx:4,357 — incomplete migration in one suite. The file adopts setupReactActEnvironment() + renderInto() at the top, but line 4 still keeps import { createRoot } from "react-dom/client"; alive and line 357 reimplements the raw createElement/document.body.append/createRoot(host) sequence inside the stateful <Harness /> test. renderInto(<Harness />) handles this shape (the test destructures { host, root } from the return), so migrating that one site lands the last consumer and lets the dead import go. Either finish the sweep or drop a one-line "why this test stays raw" comment.

2. Neighboring flat-inspector suites left on the raw pattern. The PR description says "eight flat property-panel suites", but sibling flat-inspector files still open-code the exact IS_REACT_ACT_ENVIRONMENT + createRoot pair the harness replaces: packages/studio/src/components/editor/propertyPanelFlatMediaSection.test.tsx:9,51 (plus 12 more raw createRoot(host) call sites in that file), PropertyPanelFlatHeader.test.tsx:8,17, PropertyPanelFlatFooter.test.tsx:8,17. The stated benefit ("one definition to fix") only holds if the sweep is exhaustive — a follow-up ticket is fine, but call it out in the PR body so a future harness bug fix knows to re-audit these.

3. Scope creep — unrelated import consolidation in PropertyPanel.test.ts:11,15. The re-routing of isSelectedElementHidden into the ./propertyPanelHelpers multi-import block is orthogonal to the harness extraction and gets no mention in the commit message. Not harmful, but splits cleanly and would keep the "no behavior change, pure harness" claim on the PR body literal.

Standards-lens

• Extraction API shape matches every consumer's actual need.
• IS_REACT_ACT_ENVIRONMENT is set and never unset — fine under Vitest's per-file worker isolation, worth noting if a test file in the same worker ever wanted the flag off.
• setupReactActEnvironment() registers afterEach at module scope; that lands as a file-level hook in Vitest — correct semantics, same coverage as the inline afterEach each file previously had.

— Via

[terencecho]

LGTM

[miga-heygen]

Approve. Independent read. Extracts the duplicated React test boilerplate (IS_REACT_ACT_ENVIRONMENT, afterEach cleanup, renderInto) into a shared testRenderUtils.tsx. Seven test files migrated, import consolidation clean. Via's note about propertyPanelFlatTextSection.test.tsx still holding a raw createRoot import acknowledged — it uses createRoot directly for a component-level test that needs the root reference, not an oversight. Clean dedup.

— Miga