Unittest to check Input box initial value (#5976)

Adds unit test to verify the initial value of Input widgets.
diff --git a/AUTHORS b/AUTHORS
index 223d9a9..5d0cac1 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -5,3 +5,4 @@
 
 Google Inc.
 Jim Simon <jim.j.simon@gmail.com>
+Lex Berezhny <lex@damoti.com>