diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 519978f4fb..2bac6cba58 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -326,14 +326,19 @@ static int linelen(int *has_tab)
   int save;
   int len;
 
-  /* find the first non-blank character */
+  // Get the line.  If it's empty bail out early (could be the empty string
+  // for an unloaded buffer).
   line = get_cursor_line_ptr();
+  if (*line == NUL) {
+    return 0;
+  }
+  // find the first non-blank character
   first = skipwhite(line);
 
-  /* find the character after the last non-blank character */
+  // find the character after the last non-blank character
   for (last = first + STRLEN(first);
-       last > first && ascii_iswhite(last[-1]); --last)
-    ;
+       last > first && ascii_iswhite(last[-1]); last--) {
+  }
   save = *last;
   *last = NUL;
   // Get line length.
diff --git a/src/nvim/os/time.c b/src/nvim/os/time.c
index 349a91fc1e..4b6533cd0c 100644
--- a/src/nvim/os/time.c
+++ b/src/nvim/os/time.c
@@ -176,10 +176,11 @@ char *os_ctime_r(const time_t *restrict clock, char *restrict result,
   struct tm *clock_local_ptr = os_localtime_r(clock, &clock_local);
   // MSVC returns NULL for an invalid value of seconds.
   if (clock_local_ptr == NULL) {
-    snprintf(result, result_len, "%s\n", _("(Invalid)"));
+    xstrlcpy(result, _("(Invalid)"), result_len);
   } else {
-    strftime(result, result_len, "%a %b %d %H:%M:%S %Y\n", clock_local_ptr);
+    strftime(result, result_len, _("%a %b %d %H:%M:%S %Y"), clock_local_ptr);
   }
+  xstrlcat(result, "\n", result_len);
   return result;
 }
 
diff --git a/src/nvim/po/check.vim b/src/nvim/po/check.vim
index 650c6155e2..d55d4cfa4d 100644
--- a/src/nvim/po/check.vim
+++ b/src/nvim/po/check.vim
@@ -25,6 +25,7 @@ func! GetMline()
 
   " remove '%', not used for formatting.
   let idline = substitute(idline, "'%'", '', 'g')
+  let idline = substitute(idline, "%%", '', 'g')
 
   " remove '%' used for plural forms.
   let idline = substitute(idline, '\\nPlural-Forms: .\+;\\n', '', '')
diff --git a/src/nvim/testdir/check.vim b/src/nvim/testdir/check.vim
index 57a8eb57b8..073873bcb0 100644
--- a/src/nvim/testdir/check.vim
+++ b/src/nvim/testdir/check.vim
@@ -1,6 +1,46 @@
 source shared.vim
 source term_util.vim
 
+" Command to check for the presence of a feature.
+command -nargs=1 CheckFeature call CheckFeature(<f-args>)
+func CheckFeature(name)
+  if !has(a:name)
+    throw 'Skipped: ' .. a:name .. ' feature missing'
+  endif
+endfunc
+
+" Command to check for the presence of a working option.
+command -nargs=1 CheckOption call CheckOption(<f-args>)
+func CheckOption(name)
+  if !exists('+' .. a:name)
+    throw 'Skipped: ' .. a:name .. ' option not supported'
+  endif
+endfunc
+
+" Command to check for the presence of a function.
+command -nargs=1 CheckFunction call CheckFunction(<f-args>)
+func CheckFunction(name)
+  if !exists('*' .. a:name)
+    throw 'Skipped: ' .. a:name .. ' function missing'
+  endif
+endfunc
+
+" Command to check for running on MS-Windows
+command CheckMSWindows call CheckMSWindows()
+func CheckMSWindows()
+  if !has('win32')
+    throw 'Skipped: only works on MS-Windows'
+  endif
+endfunc
+
+" Command to check for running on Unix
+command CheckUnix call CheckUnix()
+func CheckUnix()
+  if !has('unix')
+    throw 'Skipped: only works on Unix'
+  endif
+endfunc
+
 " Command to check that making screendumps is supported.
 " Caller must source screendump.vim
 command CheckScreendump call CheckScreendump()
@@ -9,3 +49,19 @@ func CheckScreendump()
     throw 'Skipped: cannot make screendumps'
   endif
 endfunc
+
+" Command to check that we can Run Vim in a terminal window
+command CheckRunVimInTerminal call CheckRunVimInTerminal()
+func CheckRunVimInTerminal()
+  if !CanRunVimInTerminal()
+    throw 'Skipped: cannot run Vim in a terminal window'
+  endif
+endfunc
+
+" Command to check that we can run the GUI
+command CheckCanRunGui call CheckCanRunGui()
+func CheckCanRunGui()
+  if !has('gui') || ($DISPLAY == "" && !has('gui_running'))
+    throw 'Skipped: cannot start the GUI'
+  endif
+endfunc
diff --git a/src/nvim/testdir/runtest.vim b/src/nvim/testdir/runtest.vim
index 4f16aa807c..765ba2cbb6 100644
--- a/src/nvim/testdir/runtest.vim
+++ b/src/nvim/testdir/runtest.vim
@@ -101,6 +101,8 @@ let &runtimepath .= ','.expand($BUILD_DIR).'/runtime/'
 " Always use forward slashes.
 set shellslash
 
+let s:t_bold = &t_md
+let s:t_normal = &t_me
 if has('win32')
   " avoid prompt that is long or contains a line break
   let $PROMPT = '$P$G'
@@ -209,7 +211,15 @@ func RunTheTest(test)
 
   let message = 'Executed ' . a:test
   if has('reltime')
-    let message ..= ' in ' .. reltimestr(reltime(func_start)) .. ' seconds'
+    let message ..= repeat(' ', 50 - len(message))
+    let time = reltime(func_start)
+    if has('float') && reltimefloat(time) > 0.1
+      let message = s:t_bold .. message
+    endif
+    let message ..= ' in ' .. reltimestr(time) .. ' seconds'
+    if has('float') && reltimefloat(time) > 0.1
+      let message ..= s:t_normal
+    endif
   endif
   call add(s:messages, message)
   let s:done += 1
@@ -277,7 +287,9 @@ func FinishTesting()
     let message = 'Executed ' . s:done . (s:done > 1 ? ' tests' : ' test')
   endif
   if s:done > 0 && has('reltime')
+    let message = s:t_bold .. message .. repeat(' ', 40 - len(message))
     let message ..= ' in ' .. reltimestr(reltime(s:start_time)) .. ' seconds'
+    let message ..= s:t_normal
   endif
   echo message
   call add(s:messages, message)
diff --git a/src/nvim/testdir/shared.vim b/src/nvim/testdir/shared.vim
index 41ff9b2bd6..6180d542ff 100644
--- a/src/nvim/testdir/shared.vim
+++ b/src/nvim/testdir/shared.vim
@@ -271,7 +271,7 @@ func GetVimCommand(...)
     let cmd = cmd . ' -u ' . name
   endif
   let cmd .= ' --headless -i NONE'
-  let cmd = substitute(cmd, 'VIMRUNTIME=.*VIMRUNTIME;', '', '')
+  let cmd = substitute(cmd, 'VIMRUNTIME=\S\+', '', '')
 
   " If using valgrind, make sure every run uses a different log file.
   if cmd =~ 'valgrind.*--log-file='
@@ -329,7 +329,3 @@ func RunVimPiped(before, after, arguments, pipecmd)
   endif
   return 1
 endfunc
-
-func CanRunGui()
-  return has('gui') && ($DISPLAY != "" || has('gui_running'))
-endfunc
diff --git a/src/nvim/testdir/test_diffmode.vim b/src/nvim/testdir/test_diffmode.vim
index a1f1dd3bab..f09a64c329 100644
--- a/src/nvim/testdir/test_diffmode.vim
+++ b/src/nvim/testdir/test_diffmode.vim
@@ -724,10 +724,140 @@ func Test_diff_lastline()
   bwipe!
 endfunc
 
+func Test_diff_screen()
+  CheckScreendump
+  CheckFeature menu
+
+  " clean up already existing swap files, just in case
+  call delete('.Xfile1.swp')
+  call delete('.Xfile2.swp')
+
+  " Test 1: Add a line in beginning of file 2
+  call WriteDiffFiles(0, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
+  let buf = RunVimInTerminal('-d Xfile1 Xfile2', {})
+  " Set autoread mode, so that Vim won't complain once we re-write the test
+  " files
+  call term_sendkeys(buf, ":set autoread\<CR>\<c-w>w:set autoread\<CR>\<c-w>w")
+
+  call VerifyBoth(buf, 'Test_diff_01', '')
+
+  " Test 2: Add a line in beginning of file 1
+  call WriteDiffFiles(buf, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
+  call VerifyBoth(buf, 'Test_diff_02', '')
+
+  " Test 3: Add a line at the end of file 2
+  call WriteDiffFiles(buf, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11])
+  call VerifyBoth(buf, 'Test_diff_03', '')
+
+  " Test 4: Add a line at the end of file 1
+  call WriteDiffFiles(buf, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
+  call VerifyBoth(buf, 'Test_diff_04', '')
+
+  " Test 5: Add a line in the middle of file 2, remove on at the end of file 1
+  call WriteDiffFiles(buf, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], [1, 2, 3, 4, 4, 5, 6, 7, 8, 9, 10])
+  call VerifyBoth(buf, 'Test_diff_05', '')
+
+  " Test 6: Add a line in the middle of file 1, remove on at the end of file 2
+  call WriteDiffFiles(buf, [1, 2, 3, 4, 4, 5, 6, 7, 8, 9, 10], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11])
+  call VerifyBoth(buf, 'Test_diff_06', '')
+
+  " Variants on test 6 with different context settings
+  call term_sendkeys(buf, ":set diffopt+=context:2\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_06.2', {})
+  call term_sendkeys(buf, ":set diffopt-=context:2\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=context:1\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_06.1', {})
+  call term_sendkeys(buf, ":set diffopt-=context:1\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=context:0\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_06.0', {})
+  call term_sendkeys(buf, ":set diffopt-=context:0\<cr>")
+
+  " Test 7 - 9: Test normal/patience/histogram diff algorithm
+  call WriteDiffFiles(buf, ['#include <stdio.h>', '', '// Frobs foo heartily', 'int frobnitz(int foo)', '{',
+      \ '    int i;', '    for(i = 0; i < 10; i++)', '    {', '        printf("Your answer is: ");',
+      \ '        printf("%d\n", foo);', '    }', '}', '', 'int fact(int n)', '{', '    if(n > 1)', '    {',
+      \ '        return fact(n-1) * n;', '    }', '    return 1;', '}', '', 'int main(int argc, char **argv)',
+      \ '{', '    frobnitz(fact(10));', '}'],
+      \ ['#include <stdio.h>', '', 'int fib(int n)', '{', '    if(n > 2)', '    {',
+      \ '        return fib(n-1) + fib(n-2);', '    }', '    return 1;', '}', '', '// Frobs foo heartily',
+      \ 'int frobnitz(int foo)', '{', '    int i;', '    for(i = 0; i < 10; i++)', '    {',
+      \ '        printf("%d\n", foo);', '    }', '}', '',
+      \ 'int main(int argc, char **argv)', '{', '    frobnitz(fib(10));', '}'])
+  call term_sendkeys(buf, ":diffupdate!\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=internal\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_07', {})
+
+  call term_sendkeys(buf, ":set diffopt+=algorithm:patience\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_08', {})
+
+  call term_sendkeys(buf, ":set diffopt+=algorithm:histogram\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_09', {})
+
+  " Test 10-11: normal/indent-heuristic
+  call term_sendkeys(buf, ":set diffopt&vim\<cr>")
+  call WriteDiffFiles(buf, ['', '  def finalize(values)', '', '    values.each do |v|', '      v.finalize', '    end'],
+      \ ['', '  def finalize(values)', '', '    values.each do |v|', '      v.prepare', '    end', '',
+      \ '    values.each do |v|', '      v.finalize', '    end'])
+  call term_sendkeys(buf, ":diffupdate!\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=internal\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_10', {})
+
+  " Leave trailing : at commandline!
+  call term_sendkeys(buf, ":set diffopt+=indent-heuristic\<cr>:\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_11', {}, 'one')
+  " shouldn't matter, if indent-algorithm comes before or after the algorithm
+  call term_sendkeys(buf, ":set diffopt&\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=indent-heuristic,algorithm:patience\<cr>:\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_11', {}, 'two')
+  call term_sendkeys(buf, ":set diffopt&\<cr>")
+  call term_sendkeys(buf, ":set diffopt+=algorithm:patience,indent-heuristic\<cr>:\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_11', {}, 'three')
+
+  " Test 12: diff the same file
+  call WriteDiffFiles(buf, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
+  call VerifyBoth(buf, 'Test_diff_12', '')
+
+  " Test 13: diff an empty file
+  call WriteDiffFiles(buf, [], [])
+  call VerifyBoth(buf, 'Test_diff_13', '')
+
+  " Test 14: test diffopt+=icase
+  call WriteDiffFiles(buf, ['a', 'b', 'cd'], ['A', 'b', 'cDe'])
+  call VerifyBoth(buf, 'Test_diff_14', " diffopt+=filler diffopt+=icase")
+
+  " Test 15-16: test diffopt+=iwhite
+  call WriteDiffFiles(buf, ['int main()', '{', '   printf("Hello, World!");', '   return 0;', '}'],
+      \ ['int main()', '{', '   if (0)', '   {', '      printf("Hello, World!");', '      return 0;', '   }', '}'])
+  call term_sendkeys(buf, ":diffupdate!\<cr>")
+  call term_sendkeys(buf, ":set diffopt&vim diffopt+=filler diffopt+=iwhite\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_15', {})
+  call term_sendkeys(buf, ":set diffopt+=internal\<cr>")
+  call VerifyScreenDump(buf, 'Test_diff_16', {})
+
+  " Test 17: test diffopt+=iblank
+  call WriteDiffFiles(buf, ['a', ' ', 'cd', 'ef', 'xxx'], ['a', 'cd', '', 'ef', 'yyy'])
+  call VerifyInternal(buf, 'Test_diff_17', " diffopt+=iblank")
+
+  " Test 18: test diffopt+=iblank,iwhite / iwhiteall / iwhiteeol
+  call VerifyInternal(buf, 'Test_diff_18', " diffopt+=iblank,iwhite")
+  call VerifyInternal(buf, 'Test_diff_18', " diffopt+=iblank,iwhiteall")
+  call VerifyInternal(buf, 'Test_diff_18', " diffopt+=iblank,iwhiteeol")
+
+  " Test 19: test diffopt+=iwhiteeol
+  call WriteDiffFiles(buf, ['a ', 'x', 'cd', 'ef', 'xx  xx', 'foo', 'bar'], ['a', 'x', 'c d', ' ef', 'xx xx', 'foo', '', 'bar'])
+  call VerifyInternal(buf, 'Test_diff_19', " diffopt+=iwhiteeol")
+
+  " Test 19: test diffopt+=iwhiteall
+  call VerifyInternal(buf, 'Test_diff_20', " diffopt+=iwhiteall")
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('Xfile1')
+  call delete('Xfile2')
+endfunc
+
 func Test_diff_with_cursorline()
-  if !CanRunVimInTerminal()
-    throw 'Skipped: cannot run Vim in a terminal window'
-  endif
+  CheckScreendump
 
   call writefile([
 	\ 'hi CursorLine ctermbg=red ctermfg=white',
@@ -751,13 +881,45 @@ func Test_diff_with_cursorline()
   call delete('Xtest_diff_cursorline')
 endfunc
 
+func Test_diff_with_syntax()
+  CheckScreendump
+
+  let lines =<< trim END
+  	void doNothing() {
+	   int x = 0;
+	   char *s = "hello";
+	   return 5;
+	}
+  END
+  call writefile(lines, 'Xprogram1.c')
+  let lines =<< trim END
+  	void doSomething() {
+	   int x = 0;
+	   char *s = "there";
+	   return 5;
+	}
+  END
+  call writefile(lines, 'Xprogram2.c')
+
+  let lines =<< trim END
+  	edit Xprogram1.c
+	diffsplit Xprogram2.c
+  END
+  call writefile(lines, 'Xtest_diff_syntax')
+  let buf = RunVimInTerminal('-S Xtest_diff_syntax', {})
+
+  call VerifyScreenDump(buf, 'Test_diff_syntax_1', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('Xtest_diff_syntax')
+  call delete('Xprogram1.c')
+  call delete('Xprogram2.c')
+endfunc
+
 func Test_diff_of_diff()
-  if !CanRunVimInTerminal()
-    throw 'Skipped: cannot run Vim in a terminal window'
-  endif
-  if !has("rightleft")
-    throw 'Skipped: rightleft not supported'
-  endif
+  CheckScreendump
+  CheckFeature rightleft
 
   call writefile([
 	\ 'call setline(1, ["aa","bb","cc","@@ -3,2 +5,7 @@","dd","ee","ff"])',
diff --git a/src/nvim/testdir/test_display.vim b/src/nvim/testdir/test_display.vim
index 1c2f5a05ff..429253a863 100644
--- a/src/nvim/testdir/test_display.vim
+++ b/src/nvim/testdir/test_display.vim
@@ -6,11 +6,12 @@
 " endif
 
 source view_util.vim
+source check.vim
+source screendump.vim
+
+func Test_display_foldcolumn()
+  CheckFeature folding
 
-func! Test_display_foldcolumn()
-  if !has("folding")
-    return
-  endif
   new
   vnew
   vert resize 25
@@ -26,10 +27,10 @@ func! Test_display_foldcolumn()
 
   call cursor(2, 1)
   norm! zt
-  let lines=ScreenLines([1,2], winwidth(0))
+  let lines = ScreenLines([1,2], winwidth(0))
   call assert_equal(expect, lines)
   set fdc=2
-  let lines=ScreenLines([1,2], winwidth(0))
+  let lines = ScreenLines([1,2], winwidth(0))
   let expect = [
         \ "  e more noise blah blah<",
         \ "  82> more stuff here    "
@@ -41,9 +42,8 @@ func! Test_display_foldcolumn()
 endfunc
 
 func! Test_display_foldtext_mbyte()
-  if !has("folding")
-    return
-  endif
+  CheckFeature folding
+
   call NewWindow(10, 40)
   call append(0, range(1,20))
   exe "set foldmethod=manual foldtext=foldtext() fillchars=fold:\u2500,vert:\u2502 fdc=2"
@@ -70,6 +70,42 @@ func! Test_display_foldtext_mbyte()
   bw!
 endfunc
 
+" check that win_ins_lines() and win_del_lines() work when t_cs is empty.
+func Test_scroll_without_region()
+  CheckScreendump
+
+  let lines =<< trim END
+    call setline(1, range(1, 20))
+    set t_cs=
+    set laststatus=2
+  END
+  call writefile(lines, 'Xtestscroll')
+  let buf = RunVimInTerminal('-S Xtestscroll', #{rows: 10})
+
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_1', {})
+
+  call term_sendkeys(buf, ":3delete\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_2', {})
+
+  call term_sendkeys(buf, ":4put\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_3', {})
+
+  call term_sendkeys(buf, ":undo\<cr>")
+  call term_sendkeys(buf, ":undo\<cr>")
+  call term_sendkeys(buf, ":set laststatus=0\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_4', {})
+
+  call term_sendkeys(buf, ":3delete\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_5', {})
+
+  call term_sendkeys(buf, ":4put\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_6', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete('Xtestscroll')
+endfunc
+
 func Test_display_listchars_precedes()
   set fillchars+=vert:\|
   call NewWindow(10, 10)
@@ -125,3 +161,26 @@ func Test_display_listchars_precedes()
   set list& listchars& wrap&
   bw!
 endfunc
+
+" Check that win_lines() works correctly with the number_only parameter=TRUE
+" should break early to optimize cost of drawing, but needs to make sure
+" that the number column is correctly highlighted.
+func Test_scroll_CursorLineNr_update()
+  CheckScreendump
+
+  let lines =<< trim END
+    hi CursorLineNr ctermfg=73 ctermbg=236
+    set nu rnu cursorline cursorlineopt=number
+    exe ":norm! o\<esc>110ia\<esc>"
+  END
+  let filename = 'Xdrawscreen'
+  call writefile(lines, filename)
+  let buf = RunVimInTerminal('-S '.filename, #{rows: 5, cols: 50})
+  call term_sendkeys(buf, "k")
+  call term_wait(buf)
+  call VerifyScreenDump(buf, 'Test_winline_rnu', {})
+
+  " clean up
+  call StopVimInTerminal(buf)
+  call delete(filename)
+endfunc
diff --git a/src/nvim/testdir/test_textformat.vim b/src/nvim/testdir/test_textformat.vim
index 75673adf0a..2223be952c 100644
--- a/src/nvim/testdir/test_textformat.vim
+++ b/src/nvim/testdir/test_textformat.vim
@@ -1,4 +1,7 @@
 " Tests for the various 'formatoptions' settings
+
+source check.vim
+
 func Test_text_format()
   enew!
 
@@ -490,6 +493,23 @@ func Test_format_list_auto()
   set fo& ai& bs&
 endfunc
 
+func Test_crash_github_issue_5095()
+  CheckFeature autocmd
+
+  " This used to segfault, see https://github.com/vim/vim/issues/5095
+  augroup testing
+    au BufNew x center
+  augroup END
+
+  next! x
+
+  bw
+  augroup testing
+    au!
+  augroup END
+  augroup! testing
+endfunc
+
 " Test for formatting multi-byte text with 'fo=t'
 func Test_tw_2_fo_t()
   new