diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 5ad1718..233ca12 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -186,6 +186,7 @@
 	    test_viminfo.res \
 	    test_viml.res \
 	    test_visual.res \
+	    test_window_id.res \
 	    test_alot.res
 
 
diff --git a/src/testdir/test_window_id.vim b/src/testdir/test_window_id.vim
new file mode 100644
index 0000000..b9e9f45
--- /dev/null
+++ b/src/testdir/test_window_id.vim
@@ -0,0 +1,71 @@
+" Test using the window ID.
+
+func Test_win_getid()
+  edit one
+  let id1 = win_getid()
+  split two
+  let id2 = win_getid()
+  split three
+  let id3 = win_getid()
+  tabnew
+  edit four
+  let id4 = win_getid()
+  split five
+  let id5 = win_getid()
+  tabnext
+
+  wincmd w
+  call assert_equal("two", expand("%"))
+  call assert_equal(id2, win_getid())
+  let nr2 = winnr()
+  wincmd w
+  call assert_equal("one", expand("%"))
+  call assert_equal(id1, win_getid())
+  let nr1 = winnr()
+  wincmd w
+  call assert_equal("three", expand("%"))
+  call assert_equal(id3, win_getid())
+  let nr3 = winnr()
+  tabnext
+  call assert_equal("five", expand("%"))
+  call assert_equal(id5, win_getid())
+  let nr5 = winnr()
+  wincmd w
+  call assert_equal("four", expand("%"))
+  call assert_equal(id4, win_getid())
+  let nr4 = winnr()
+  tabnext
+
+  exe nr1 . "wincmd w"
+  call assert_equal(id1, win_getid())
+  exe nr2 . "wincmd w"
+  call assert_equal(id2, win_getid())
+  exe nr3 . "wincmd w"
+  call assert_equal(id3, win_getid())
+  tabnext
+  exe nr4 . "wincmd w"
+  call assert_equal(id4, win_getid())
+  exe nr5 . "wincmd w"
+  call assert_equal(id5, win_getid())
+
+  call win_gotoid(id2)
+  call assert_equal("two", expand("%"))
+  call win_gotoid(id4)
+  call assert_equal("four", expand("%"))
+  call win_gotoid(id1)
+  call assert_equal("one", expand("%"))
+  call win_gotoid(id5)
+  call assert_equal("five", expand("%"))
+
+  call assert_equal(0, win_id2win(9999))
+  call assert_equal(nr5, win_id2win(id5))
+  call assert_equal(0, win_id2win(id1))
+  tabnext
+  call assert_equal(nr1, win_id2win(id1))
+
+  call assert_equal([0, 0], win_id2tabwin(9999))
+  call assert_equal([1, nr2], win_id2tabwin(id2))
+  call assert_equal([2, nr4], win_id2tabwin(id4))
+
+  only!
+endfunc