docs(spanner): migrate quickstart sample

Migrates quickstart.js from googleapis/nodejs-spanner and enables its test suite in spanner.test.js.

Author: sakthivelmanii

spanner/quickstart.js

@@ -0,0 +1,46 @@
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+'use strict';
+
+async function quickstart(
+  projectId = 'YOUR-PROJECT-ID', // Your Google Cloud Platform project ID
+  instanceId = 'my-instance', // Your Cloud Spanner instance ID
+  databaseId = 'my-database', // Your Cloud Spanner database ID
+) {
+  // [START spanner_quickstart]
+  // Imports the Google Cloud client library
+  const {Spanner} = require('@google-cloud/spanner');
+
+  // Creates a client
+  const spanner = new Spanner({projectId});
+
+  // Gets a reference to a Cloud Spanner instance and database
+  const instance = spanner.instance(instanceId);
+  const database = instance.database(databaseId);
+
+  // The query to execute
+  const query = {
+    sql: 'SELECT 1',
+  };
+
+  // Execute a simple SQL statement
+  const [rows] = await database.run(query);
+  console.log(`Query: ${rows.length} found.`);
+  rows.forEach(row => console.log(row));
+  // [END spanner_quickstart]
+}
+
+const args = process.argv.slice(2);
+quickstart(...args).catch(console.error);

spanner/system-test/spanner.test.js

@@ -1,4 +1,4 @@
-// Copyright 2024 Google LLC
+// Copyright 2026 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -585,7 +585,7 @@ describe('Autogenerated Admin Clients', () => {
     });
   });
 
-  describe.skip('quickstart', () => {
+  describe('quickstart', () => {
     // Running the quickstart test in here since there's already a spanner
     // instance and database set up at this point.
     it('should query a table', async () => {