diff --git a/runtime/doc/testing.txt b/runtime/doc/testing.txt
index 6fd2d45..db505e7 100644
--- a/runtime/doc/testing.txt
+++ b/runtime/doc/testing.txt
@@ -1,4 +1,4 @@
-*testing.txt*	For Vim version 8.2.  Last change: 2021 Apr 02
+*testing.txt*	For Vim version 8.2.  Last change: 2021 Jun 21
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -78,6 +78,30 @@
 
 		Can also be used as a |method|: >
 			GetName()->test_getvalue()
+<
+						*test_gui_mouse_event()*
+test_gui_mouse_event({button}, {row}, {col}, {multiclick}, {modifiers})
+		Inject a mouse button click event.  This function works only
+		when GUI is running.
+		The supported values for {button} are:
+			0	right mouse button
+			1	middle mouse button
+			2	left mouse button
+			3	mouse button release
+			4	scroll wheel down
+			5	scroll wheel up
+			6	scroll wheel left
+			7	scroll wheel right
+		{row} and {col} specify the location of the mouse click.
+		To inject a multiclick event, set {multiclick} to 1.
+		The supported values for {modifiers} are:
+			4	shift is pressed
+			8	alt is pressed
+			16	ctrl is pressed
+		After injecting the mouse event you probably should call
+		|feedkeys()| to have them processed, e.g.: >
+			call feedkeys("y", 'Lx!')
+
 
 test_ignore_error({expr})			 *test_ignore_error()*
 		Ignore any error containing {expr}.  A normal message is given