Add unit test for the naming of our destination migration index

x-pack/plugins/security_solution/server/lib/detection_engine/migrations/create_signals_migration_index.test.ts

@@ -0,0 +1,25 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { ElasticsearchClient } from 'src/core/server';
+import { elasticsearchServiceMock } from 'src/core/server/mocks';
+import { createSignalsMigrationIndex } from './create_signals_migration_index';
+
+describe('getMigrationStatus', () => {
+  let esClient: ElasticsearchClient;
+
+  beforeEach(() => {
+    esClient = elasticsearchServiceMock.createElasticsearchClient();
+  });
+
+  it('creates an index suffixed with the template version', async () => {
+    await createSignalsMigrationIndex({ esClient, index: 'my-signals-index', version: 4 });
+
+    expect(esClient.indices.create).toHaveBeenCalledWith(
+      expect.objectContaining({ index: 'my-signals-index-r000004' })
+    );
+  });
+});