add: unit and integration testing

app/node_modules/babel-jest/build/index.d.ts

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {TransformOptions} from '@babel/core';
+import {SyncTransformer, TransformerCreator} from '@jest/transform';
+
+export declare const createTransformer: TransformerCreator<
+  SyncTransformer<TransformerConfig>,
+  TransformerConfig
+>;
+
+export declare interface TransformerConfig extends TransformOptions {
+  excludeJestPreset?: boolean;
+}
+
+declare const transformerFactory: {
+  createTransformer: TransformerCreator<
+    SyncTransformer<TransformerConfig>,
+    TransformerConfig
+  >;
+};
+export default transformerFactory;