diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 50b7fb2..d598966 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -3365,6 +3365,7 @@
         \ wincol: 1,
         \ line: 1,
         \ column: 1,
+        \ coladd: 0,
         \ }, getmousepos())
   call test_setmouse(1, 2)
   call assert_equal(#{
@@ -3375,6 +3376,7 @@
         \ wincol: 2,
         \ line: 1,
         \ column: 1,
+        \ coladd: 1,
         \ }, getmousepos())
   call test_setmouse(1, 8)
   call assert_equal(#{
@@ -3385,6 +3387,7 @@
         \ wincol: 8,
         \ line: 1,
         \ column: 1,
+        \ coladd: 7,
         \ }, getmousepos())
   call test_setmouse(1, 9)
   call assert_equal(#{
@@ -3395,6 +3398,7 @@
         \ wincol: 9,
         \ line: 1,
         \ column: 2,
+        \ coladd: 0,
         \ }, getmousepos())
   call test_setmouse(1, 12)
   call assert_equal(#{
@@ -3405,6 +3409,7 @@
         \ wincol: 12,
         \ line: 1,
         \ column: 2,
+        \ coladd: 3,
         \ }, getmousepos())
   call test_setmouse(1, 25)
   call assert_equal(#{
@@ -3415,6 +3420,29 @@
         \ wincol: 25,
         \ line: 1,
         \ column: 4,
+        \ coladd: 0,
+        \ }, getmousepos())
+  call test_setmouse(1, 28)
+  call assert_equal(#{
+        \ screenrow: 1,
+        \ screencol: 28,
+        \ winid: win_getid(),
+        \ winrow: 1,
+        \ wincol: 28,
+        \ line: 1,
+        \ column: 7,
+        \ coladd: 0,
+        \ }, getmousepos())
+  call test_setmouse(1, 29)
+  call assert_equal(#{
+        \ screenrow: 1,
+        \ screencol: 29,
+        \ winid: win_getid(),
+        \ winrow: 1,
+        \ wincol: 29,
+        \ line: 1,
+        \ column: 8,
+        \ coladd: 0,
         \ }, getmousepos())
   call test_setmouse(1, 50)
   call assert_equal(#{
@@ -3425,6 +3453,7 @@
         \ wincol: 50,
         \ line: 1,
         \ column: 8,
+        \ coladd: 21,
         \ }, getmousepos())
 
   " If the mouse is positioned past the last buffer line, "line" and "column"
@@ -3438,6 +3467,7 @@
         \ wincol: 25,
         \ line: 1,
         \ column: 4,
+        \ coladd: 0,
         \ }, getmousepos())
   call test_setmouse(2, 50)
   call assert_equal(#{
@@ -3448,6 +3478,7 @@
         \ wincol: 50,
         \ line: 1,
         \ column: 8,
+        \ coladd: 21,
         \ }, getmousepos())
   bwipe!
 endfunc