patch 8.2.0712: various code not fully tested

Problem:    Various code not fully tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #6049)
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 02b6585..a8506a8 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -570,6 +570,12 @@
   " invalid memory.
   call tolower("\xC0\x80\xC0")
   call tolower("123\xC0\x80\xC0")
+
+  " Test in latin1 encoding
+  let save_enc = &encoding
+  set encoding=latin1
+  call assert_equal("abc", tolower("ABC"))
+  let &encoding = save_enc
 endfunc
 
 func Test_toupper()
@@ -641,6 +647,12 @@
   " invalid memory.
   call toupper("\xC0\x80\xC0")
   call toupper("123\xC0\x80\xC0")
+
+  " Test in latin1 encoding
+  let save_enc = &encoding
+  set encoding=latin1
+  call assert_equal("ABC", toupper("abc"))
+  let &encoding = save_enc
 endfunc
 
 func Test_tr()
@@ -1160,6 +1172,10 @@
 
   call assert_equal(0, filewritable('doesnotexist'))
 
+  call mkdir('Xdir')
+  call assert_equal(2, filewritable('Xdir'))
+  call delete('Xdir', 'd')
+
   call delete('Xfilewritable')
   bw!
 endfunc
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index dec8288..ce925d8 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -269,6 +269,7 @@
   " Expand terminal options.
   call feedkeys(":set t_A\<C-A>\<C-B>\"\<CR>", 'tx')
   call assert_equal('"set t_AB t_AF t_AL', @:)
+  call assert_fails('call feedkeys(":set <t_afoo>=\<C-A>\<CR>", "xt")', 'E474:')
 
   " Expand directories.
   call feedkeys(":set cdpath=./\<C-A>\<C-B>\"\<CR>", 'tx')
diff --git a/src/testdir/test_system.vim b/src/testdir/test_system.vim
index e69a045..d597873 100644
--- a/src/testdir/test_system.vim
+++ b/src/testdir/test_system.vim
@@ -143,3 +143,41 @@
     call delete('Xdir with spaces', 'rf')
   endtry
 endfunc
+
+" Test for 'shellxquote'
+func Test_Shellxquote()
+  CheckUnix
+
+  let save_shell = &shell
+  let save_sxq = &shellxquote
+  let save_sxe = &shellxescape
+
+  call writefile(['#!/bin/sh', 'echo "Cmd: [$*]" > Xlog'], 'Xtestshell')
+  call setfperm('Xtestshell', "r-x------")
+  set shell=./Xtestshell
+
+  set shellxquote=\\"
+  call feedkeys(":!pwd\<CR>\<CR>", 'xt')
+  call assert_equal(['Cmd: [-c "pwd"]'], readfile('Xlog'))
+
+  set shellxquote=(
+  call feedkeys(":!pwd\<CR>\<CR>", 'xt')
+  call assert_equal(['Cmd: [-c (pwd)]'], readfile('Xlog'))
+
+  set shellxquote=\\"(
+  call feedkeys(":!pwd\<CR>\<CR>", 'xt')
+  call assert_equal(['Cmd: [-c "(pwd)"]'], readfile('Xlog'))
+
+  set shellxescape=\"&<<()@^
+  set shellxquote=(
+  call feedkeys(":!pwd\"&<<{}@^\<CR>\<CR>", 'xt')
+  call assert_equal(['Cmd: [-c (pwd^"^&^<^<{}^@^^)]'], readfile('Xlog'))
+
+  let &shell = save_shell
+  let &shellxquote = save_sxq
+  let &shellxescape = save_sxe
+  call delete('Xtestshell')
+  call delete('Xlog')
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/testdir/test_termcodes.vim b/src/testdir/test_termcodes.vim
index 13770c6..49262f5 100644
--- a/src/testdir/test_termcodes.vim
+++ b/src/testdir/test_termcodes.vim
@@ -1371,4 +1371,30 @@
   set timeoutlen&
 endfunc
 
+" Test for translation of special key codes (<xF1>, <xF2>, etc.)
+func Test_Keycode_Tranlsation()
+  let keycodes = [
+        \ ["<xUp>", "<Up>"],
+        \ ["<xDown>", "<Down>"],
+        \ ["<xLeft>", "<Left>"],
+        \ ["<xRight>", "<Right>"],
+        \ ["<xHome>", "<Home>"],
+        \ ["<xEnd>", "<End>"],
+        \ ["<zHome>", "<Home>"],
+        \ ["<zEnd>", "<End>"],
+        \ ["<xF1>", "<F1>"],
+        \ ["<xF2>", "<F2>"],
+        \ ["<xF3>", "<F3>"],
+        \ ["<xF4>", "<F4>"],
+        \ ["<S-xF1>", "<S-F1>"],
+        \ ["<S-xF2>", "<S-F2>"],
+        \ ["<S-xF3>", "<S-F3>"],
+        \ ["<S-xF4>", "<S-F4>"]]
+  for [k1, k2] in keycodes
+    exe "nnoremap " .. k1 .. " 2wx"
+    call assert_true(maparg(k1, 'n', 0, 1).lhs == k2)
+    exe "nunmap " .. k1
+  endfor
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index d63cc8b..f9ce53b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    712,
+/**/
     711,
 /**/
     710,