vim-patch:8.2.3510: changes are only detected with one second accuracy

Problem:    Changes are only detected with one second accuracy.
Solution:   Use the nanosecond time if possible.  (Leah Neukirchen,
            closes vim/vim#8873, closes vim/vim#8875)
https://github.com/vim/vim/commit/0a7984af5601323fae7b3398f05a48087db7b767

In Nvim Test_checktime_fast() is also flaky. Add a delay to avoid that.

1 files changed, 36 insertions, 0 deletions

diff --git a/src/nvim/testdir/test_stat.vim b/src/nvim/testdir/test_stat.vim
index 170358e023..a6fe31b85a 100644
--- a/src/nvim/testdir/test_stat.vim
+++ b/src/nvim/testdir/test_stat.vim
@@ -1,5 +1,7 @@
 " Tests for stat functions and checktime
 
+source check.vim
+
 func CheckFileTime(doSleep)
   let fnames = ['Xtest1.tmp', 'Xtest2.tmp', 'Xtest3.tmp']
   let times = []
@@ -74,6 +76,40 @@ func Test_checktime()
   call delete(fname)
 endfunc
 
+func Test_checktime_fast()
+  CheckFeature nanotime
+
+  let fname = 'Xtest.tmp'
+
+  let fl = ['Hello World!']
+  call writefile(fl, fname)
+  set autoread
+  exec 'e' fname
+  let fl = readfile(fname)
+  let fl[0] .= ' - checktime'
+  sleep 10m  " make test less flaky in Nvim
+  call writefile(fl, fname)
+  checktime
+  call assert_equal(fl[0], getline(1))
+
+  call delete(fname)
+endfunc
+
+func Test_autoread_fast()
+  CheckFeature nanotime
+
+  new Xautoread
+  set autoread
+  call setline(1, 'foo')
+
+  w!
+  silent !echo bar > Xautoread
+  checktime
+
+  call assert_equal('bar', trim(getline(1)))
+  call delete('Xautoread')
+endfunc
+
 func Test_autoread_file_deleted()
   new Xautoread
   set autoread