feature: execute load()/unload() methods found in _pre.ts files

tests/10_test_preloaders.test.ts

@@ -0,0 +1,36 @@
+import * as asserts from '@std/assert';
+import { EPHEMERAL_SERVER, get_ephemeral_listen_server } from './helpers.ts';
+
+Deno.test({
+	name: 'check that _preload.ts files work',
+	permissions: {
+		env: true,
+		read: true,
+		write: true,
+		net: true
+	},
+	fn: async () => {
+		let test_server_info: EPHEMERAL_SERVER | null = null;
+		const cwd = Deno.cwd();
+
+		try {
+			Deno.chdir('./tests/www');
+			test_server_info = await get_ephemeral_listen_server();
+
+			const preloader_env_setting = Deno.env.get('SERVERUS_PRELOADED_TEST');
+			asserts.assertEquals(preloader_env_setting, 'true');
+
+			await test_server_info.server.stop();
+
+			const preloader_env_setting_after_unload = Deno.env.get('SERVERUS_PRELOADED_TEST');
+			asserts.assertEquals(preloader_env_setting_after_unload, undefined);
+
+			test_server_info = null;
+		} finally {
+			Deno.chdir(cwd);
+			if (test_server_info) {
+				await test_server_info?.server?.stop();
+			}
+		}
+	}
+});