Addressed comments

Author: maneesht

packages/database/test/helpers/util.ts

@@ -15,7 +15,6 @@
  * limitations under the License.
  */
 
-import { v4 as uuidv4 } from 'uuid';
 
 import { Database, ref } from '../../src';
 import { ConnectionTarget } from '../../src/api/test_access';
@@ -80,6 +79,18 @@ export function waitFor(waitTimeInMS: number) {
   return new Promise(resolve => setTimeout(resolve, waitTimeInMS));
 }
 
+/**
+ * Copied from https://stackoverflow.com/a/2117523
+ * TODO: extract this into @firebase/util
+ */
+export function uuidv4(): string {
+  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, c => {
+    const r = (Math.random() * 16) | 0,
+      v = c === 'x' ? r : (r & 0x3) | 0x8;
+    return v.toString(16);
+  });
+}
+
 // Creates a unique reference using uuid
 export function getUniqueRef(db: Database) {
   const path = uuidv4();