2 files changed, 32 insertions, 0 deletions
diff --git a/test/functional/api/highlight_spec.lua b/test/functional/api/highlight_spec.lua
index a9d4c72d31..daf20c006c 100644
--- a/test/functional/api/highlight_spec.lua
+++ b/test/functional/api/highlight_spec.lua
@@ -7,6 +7,7 @@ local meths = helpers.meths
 local funcs = helpers.funcs
 local pcall_err = helpers.pcall_err
 local ok = helpers.ok
+local assert_alive = helpers.assert_alive
 
 describe('API: highlight',function()
   local expected_rgb = {
@@ -145,4 +146,15 @@ describe('API: highlight',function()
     eq({foreground=tonumber("0x888888"), background=tonumber("0x888888")},
        meths.get_hl_by_name("Shrubbery", true))
   end)
+
+  it("nvim_buf_add_highlight to other buffer doesn't crash if undo is disabled #12873", function()
+    command('vsplit file')
+    local err, _ = pcall(meths.buf_set_option, 1, 'undofile', false)
+    eq(true, err)
+    err, _ = pcall(meths.buf_set_option, 1, 'undolevels', -1)
+    eq(true, err)
+    err, _ = pcall(meths.buf_add_highlight, 1, -1, 'Question', 0, 0, -1)
+    eq(true, err)
+    assert_alive()
+  end)
 end)
diff --git a/test/functional/ui/inccommand_spec.lua b/test/functional/ui/inccommand_spec.lua
index 74e85212c8..16c5477ee4 100644
--- a/test/functional/ui/inccommand_spec.lua
+++ b/test/functional/ui/inccommand_spec.lua
@@ -2750,6 +2750,26 @@ it(':substitute with inccommand, timer-induced :redraw #9777', function()
   ]])
 end)
 
+it(":substitute doesn't crash with inccommand, if undo is empty #12932", function()
+  local screen = Screen.new(10,5)
+  clear()
+  command('set undolevels=-1')
+  common_setup(screen, 'split', 'test')
+  feed(':%s/test')
+  sleep(100)
+  feed('/')
+  sleep(100)
+  feed('f')
+  screen:expect([[
+  {12:f}           |
+  {15:~           }|
+  {15:~           }|
+  {15:~           }|
+  :%s/test/f^  |
+  ]])
+  assert_alive()
+end)
+
 it('long :%s/ with inccommand does not collapse cmdline', function()
   local screen = Screen.new(10,5)
   clear()