test(vitest-plugin): add with-vitest-v5 example

Benchmark the plugin against Vitest 5 in CI the way the v3 and v4 examples
do for their majors, using the `bench` fixture and `bench.compare()`.

Refs COD-2931
Co-Authored-By: Claude <noreply@anthropic.com>

Author: GuillaumeLagrange

examples/with-vitest-v5/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "with-vitest-v5",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "bench-vitest": "vitest bench --run"
+  },
+  "devDependencies": {
+    "@codspeed/vitest-plugin": "workspace:*",
+    "typescript": "^5.1.3",
+    "vitest": "^5.0.0"
+  },
+  "dependenciesMeta": {
+    "@codspeed/vitest-plugin": {
+      "injected": true
+    }
+  }
+}

examples/with-vitest-v5/src/fibonacci.bench.ts

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+import { describe, test } from "vitest";
+import {
+  iterativeFibonacci as iterativeFibonacciExport,
+  recursiveFibonacci as recursiveFibonacciExport,
+} from "./fibonacci";
+
+// Imports are getters under Vite's module runner; read them once, outside the
+// measured loop.
+const recursiveFibonacci = recursiveFibonacciExport;
+const iterativeFibonacci = iterativeFibonacciExport;
+
+describe("fibonacci", () => {
+  test("fibo 15", async ({ bench }) => {
+    await bench.compare(
+      bench("recursive", () => {
+        recursiveFibonacci(15);
+      }),
+      bench("iterative", () => {
+        iterativeFibonacci(15);
+      }),
+    );
+  });
+
+  test("fibo 20", async ({ bench }) => {
+    await bench.compare(
+      bench("recursive", () => {
+        recursiveFibonacci(20);
+      }),
+      bench("iterative", () => {
+        iterativeFibonacci(20);
+      }),
+    );
+  });
+});

examples/with-vitest-v5/src/fibonacci.ts

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+export function recursiveFibonacci(n: number): number {
+  if (n < 2) {
+    return n;
+  }
+  return recursiveFibonacci(n - 1) + recursiveFibonacci(n - 2);
+}
+
+export function iterativeFibonacci(n: number): number {
+  let a = 0;
+  let b = 1;
+  for (let i = 0; i < n; i++) {
+    const temp = a + b;
+    a = b;
+    b = temp;
+  }
+  return a;
+}

examples/with-vitest-v5/tsconfig.json

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+{
+  "compilerOptions": {
+    "lib": ["es2023"],
+    "module": "ESNext",
+    "verbatimModuleSyntax": true,
+    "target": "es2022",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "moduleResolution": "Node"
+  }
+}

examples/with-vitest-v5/vitest.config.ts

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+import codspeedPlugin from "@codspeed/vitest-plugin";
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  plugins: [codspeedPlugin()],
+});