Fix double ScheduleModule.forRoot() registration doubling every cron/interval job (v0.21.7)

src/battery/battery.module.ts

@@ -1,10 +1,9 @@
 import { Module } from '@nestjs/common';
-import { ScheduleModule } from '@nestjs/schedule';
 import { MeshModule } from '../mesh/mesh.module.js';
 import { BatteryAlertService } from './battery.service.js';
 
 @Module({
-  imports: [ScheduleModule.forRoot(), MeshModule],
+  imports: [MeshModule],
   providers: [BatteryAlertService],
   exports: [BatteryAlertService],
 })

src/schedule-singleton.spec.ts

@@ -0,0 +1,28 @@
+import { readdirSync, readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { describe, expect, it } from 'vitest';
+
+const srcDir = fileURLToPath(new URL('.', import.meta.url));
+
+function moduleFiles(dir: string): string[] {
+  return readdirSync(dir, { withFileTypes: true }).flatMap((entry) =>
+    entry.isDirectory()
+      ? moduleFiles(join(dir, entry.name))
+      : entry.name.endsWith('.module.ts')
+        ? [join(dir, entry.name)]
+        : [],
+  );
+}
+
+describe('ScheduleModule.forRoot single registration', () => {
+  // Regression guard (v0.21.7): each forRoot() call creates its own ScheduleExplorer that scans all providers, so a second call made every @Cron/@Interval job fire twice.
+  it('appears exactly once across all src/**/*.module.ts', () => {
+    const hits = moduleFiles(srcDir).flatMap((file) =>
+      (
+        readFileSync(file, 'utf8').match(/ScheduleModule\.forRoot\(/g) ?? []
+      ).map(() => file.slice(srcDir.length)),
+    );
+    expect(hits).toHaveLength(1);
+  });
+});