test: trim test startup overhead

test/plugin-extension-import-boundary.test.ts

@@ -1,14 +1,13 @@
-import { execFileSync } from "node:child_process";
 import { readFileSync } from "node:fs";
 import path from "node:path";
 import { describe, expect, it } from "vitest";
 import {
   collectPluginExtensionImportBoundaryInventory,
   diffInventory,
+  main,
 } from "../scripts/check-plugin-extension-import-boundary.mjs";
 
 const repoRoot = process.cwd();
-const scriptPath = path.join(repoRoot, "scripts", "check-plugin-extension-import-boundary.mjs");
 const baselinePath = path.join(
   repoRoot,
   "test",
@@ -20,6 +19,27 @@ function readBaseline() {
   return JSON.parse(readFileSync(baselinePath, "utf8"));
 }
 
+function createCapturedIo() {
+  let stdout = "";
+  let stderr = "";
+  return {
+    io: {
+      stdout: {
+        write(chunk) {
+          stdout += String(chunk);
+        },
+      },
+      stderr: {
+        write(chunk) {
+          stderr += String(chunk);
+        },
+      },
+    },
+    readStdout: () => stdout,
+    readStderr: () => stderr,
+  };
+}
+
 describe("plugin extension import boundary inventory", () => {
   it("keeps dedicated web-search registry shims out of the remaining inventory", async () => {
     const inventory = await collectPluginExtensionImportBoundaryInventory();
@@ -65,12 +85,12 @@ describe("plugin extension import boundary inventory", () => {
     expect(diffInventory(expected, actual)).toEqual({ missing: [], unexpected: [] });
   });
 
-  it("script json output matches the baseline exactly", () => {
-    const stdout = execFileSync(process.execPath, [scriptPath, "--json"], {
-      cwd: repoRoot,
-      encoding: "utf8",
-    });
+  it("script json output matches the baseline exactly", async () => {
+    const captured = createCapturedIo();
+    const exitCode = await main(["--json"], captured.io);
 
-    expect(JSON.parse(stdout)).toEqual(readBaseline());
+    expect(exitCode).toBe(0);
+    expect(captured.readStderr()).toBe("");
+    expect(JSON.parse(captured.readStdout())).toEqual(readBaseline());
   });
 });