diff --git a/runtime/doc/testing.txt b/runtime/doc/testing.txt
index 6998a6e..7e8e8b9 100644
--- a/runtime/doc/testing.txt
+++ b/runtime/doc/testing.txt
@@ -94,6 +94,7 @@
 		    "findrepl"  search and replace text.
 		    "mouse"	mouse button click event.
 		    "scrollbar" move or drag the scrollbar.
+		    "sendevent" send a low-level GUI event.
 		    "tabline"	select a tab page by mouse click.
 		    "tabmenu"	select a tabline menu entry.
 
@@ -177,6 +178,15 @@
 		    dragging:	1 to drag the scrollbar and 0 to click in the
 				scrollbar.
 
+		"sendevent":
+		  Send a low-level GUI event (e.g. key-up or down).
+		  Currently only supported on MS-Windows.
+		  The supported items in {args} are:
+		    event:	The supported string values are:
+				    keyup   generate a keyup event
+				    keydown generate a keydown event
+		    keycode:    Keycode to use for a keyup or a keydown event.
+
 		"tabline":
 		  Inject a mouse click event on the tabline to select a
 		  tabpage. The supported items in {args} are: