1 files changed, 68 insertions, 0 deletions
diff --git a/test/functional/ui/output_spec.lua b/test/functional/ui/output_spec.lua
new file mode 100644
index 0000000000..33086a61b1
--- /dev/null
+++ b/test/functional/ui/output_spec.lua
@@ -0,0 +1,68 @@
+local session = require('test.functional.helpers')(after_each)
+local child_session = require('test.functional.terminal.helpers')
+
+if session.pending_win32(pending) then return end
+
+describe("shell command :!", function()
+  local screen
+  before_each(function()
+    session.clear()
+    screen = child_session.screen_setup(0, '["'..session.nvim_prog..
+      '", "-u", "NONE", "-i", "NONE", "--cmd", "set noswapfile"]')
+    screen:expect([[
+      {1: }                                                 |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]])
+  end)
+
+  after_each(function()
+    child_session.feed_data("\3") -- Ctrl-C
+    screen:detach()
+  end)
+
+  it("displays output without LF/EOF. #4646 #4569 #3772", function()
+    -- NOTE: We use a child nvim (within a :term buffer)
+    --       to avoid triggering a UI flush.
+    child_session.feed_data(":!printf foo; sleep 200\n")
+    screen:expect([[
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name]                                         }|
+      :!printf foo; sleep 200                           |
+                                                        |
+      foo                                               |
+      {3:-- TERMINAL --}                                    |
+    ]])
+  end)
+
+  it("throttles shell-command output greater than ~10KB", function()
+    if os.getenv("TRAVIS") and session.os_name() == "osx" then
+      pending("[Unreliable on Travis macOS.]", function() end)
+      return
+    end
+
+    screen.timeout = 20000  -- Avoid false failure on slow systems.
+    child_session.feed_data(
+      ":!for i in $(seq 2 3000); do echo XXXXXXXXXX $i; done\n")
+
+    -- If we observe any line starting with a dot, then throttling occurred.
+    screen:expect("\n.", nil, nil, nil, true)
+
+    -- Final chunk of output should always be displayed, never skipped.
+    -- (Throttling is non-deterministic, this test is merely a sanity check.)
+    screen:expect([[
+      XXXXXXXXXX 2996                                   |
+      XXXXXXXXXX 2997                                   |
+      XXXXXXXXXX 2998                                   |
+      XXXXXXXXXX 2999                                   |
+      XXXXXXXXXX 3000                                   |
+      {10:Press ENTER or type command to continue}{1: }          |
+      {3:-- TERMINAL --}                                    |
+    ]])
+  end)
+end)