1 files changed, 55 insertions, 0 deletions
diff --git a/test/functional/terminal/tui_spec.lua b/test/functional/terminal/tui_spec.lua
index efa65b7441..80df336cc4 100644
--- a/test/functional/terminal/tui_spec.lua
+++ b/test/functional/terminal/tui_spec.lua
@@ -2939,6 +2939,61 @@ describe('TUI', function()
     end)
   end)
 
+  it('does not query the terminal for truecolor support if $COLORTERM is set', function()
+    clear()
+    exec_lua([[
+      vim.api.nvim_create_autocmd('TermRequest', {
+        callback = function(args)
+          local req = args.data
+          vim.g.termrequest = req
+          local xtgettcap = req:match('^\027P%+q([%x;]+)$')
+          if xtgettcap then
+            local t = {}
+            for cap in vim.gsplit(xtgettcap, ';') do
+              local resp = string.format('\027P1+r%s\027\\', xtgettcap)
+              vim.api.nvim_chan_send(vim.bo[args.buf].channel, resp)
+              t[vim.text.hexdecode(cap)] = true
+            end
+            vim.g.xtgettcap = t
+            return true
+          elseif req:match('^\027P$qm\027\\$') then
+            vim.g.decrqss = true
+          end
+        end,
+      })
+    ]])
+
+    local child_server = new_pipename()
+    screen = tt.setup_child_nvim({
+      '--listen',
+      child_server,
+      '-u',
+      'NONE',
+      '-i',
+      'NONE',
+    }, {
+      env = {
+        VIMRUNTIME = os.getenv('VIMRUNTIME'),
+        -- With COLORTERM=256, Nvim should not query the terminal and should not set 'tgc'
+        COLORTERM = '256',
+        TERM = 'xterm-256colors',
+      },
+    })
+
+    screen:expect({ any = '%[No Name%]' })
+
+    local child_session = n.connect(child_server)
+    retry(nil, 1000, function()
+      local xtgettcap = eval("get(g:, 'xtgettcap', {})")
+      eq(nil, xtgettcap['Tc'])
+      eq(nil, xtgettcap['RGB'])
+      eq(nil, xtgettcap['setrgbf'])
+      eq(nil, xtgettcap['setrgbb'])
+      eq(0, eval([[get(g:, 'decrqss')]]))
+      eq({ true, 0 }, { child_session:request('nvim_eval', '&termguicolors') })
+    end)
+  end)
+
   it('queries the terminal for OSC 52 support', function()
     clear()
     exec_lua([[