functests: Make test more robust

test/functional/terminal/edit_spec.lua

@@ -10,6 +10,12 @@ local clear = helpers.clear
 local eq = helpers.eq
 
 describe(':edit term://*', function()
+  local get_screen = function(columns, lines)
+    local scr = screen.new(columns, lines)
+    scr:attach(false)
+    return scr
+  end
+
   before_each(function()
     clear()
     meths.set_option('shell', nvim_dir .. '/shell-test')
@@ -26,6 +32,8 @@ describe(':edit term://*', function()
   end)
 
   it('runs TermOpen early enough to respect terminal_scrollback_buffer_size', function()
+    local columns, lines = 20, 4
+    local scr = get_screen(columns, lines)
     local rep = 'a'
     meths.set_option('shellcmdflag', 'REP ' .. rep)
     local rep_size = rep:byte()
@@ -40,12 +48,29 @@ describe(':edit term://*', function()
     -- I have no idea why there is + 4 needed. But otherwise it works fine with 
     -- different scrollbacks.
     local shift = -4
-    for i = (rep_size - 1 - sb - winheight - shift),(rep_size - 1) do
-      bufcontents[#bufcontents + 1] = ('%d: foobar'):format(i)
+    local buf_cont_start = rep_size - 1 - sb - winheight - shift
+    local bufline = function(i) return ('%d: foobar'):format(i) end
+    for i = buf_cont_start,(rep_size - 1) do
+      bufcontents[#bufcontents + 1] = bufline(i)
     end
     bufcontents[#bufcontents + 1] = ''
     bufcontents[#bufcontents + 1] = '[Process exited 0]'
-    command('sleep 500m')
+    -- Do not ask me why displayed screen is one line *before* buffer
+    -- contents: buffer starts with 87:, screen with 86:.
+    local exp_screen = '\n'
+    local did_cursor = false
+    local shift = 10
+    for i = 0,(winheight - 1) do
+      local line = bufline(buf_cont_start + i - 1)
+      exp_screen = (exp_screen
+                    .. (did_cursor and '' or '^')
+                    .. line
+                    .. (' '):rep(columns - #line)
+                    .. '|\n')
+      did_cursor = true
+    end
+    exp_screen = exp_screen .. (' '):rep(columns) .. '|\n'
+    scr:expect(exp_screen)
     eq(bufcontents, curbufmeths.get_line_slice(1, -1, true, true))
   end)
 end)