test: select after upsert

Author: jwelmac

test/mock_supabase_http_client_test.dart

@@ -50,6 +50,20 @@ void main() {
       expect(postsUfterUpdate.first, {'id': 1, 'title': 'Updated post'});
     });
 
+    test('Upsert then select', () async {
+      // Test upserting a record
+      await mockSupabase
+          .from('posts')
+          .upsert({'id': 1, 'title': 'Initial post'});
+      final posts = await mockSupabase.from('posts').select();
+      expect(posts.first, {'id': 1, 'title': 'Initial post'});
+      final postsAfterUpdate = await mockSupabase
+          .from('posts')
+          .upsert({'id': 1, 'title': 'Updated post'}).select();
+      expect(postsAfterUpdate.length, 1);
+      expect(postsAfterUpdate.first, {'id': 1, 'title': 'Updated post'});
+    });
+
     test('Update', () async {
       // Test updating a record
       await mockSupabase