vim-patch:8.2.1505: not all file read and writecode is tested

Problem:    Not all file read and writecode is tested.
Solution:   Add a few tests. (Dominique Pellé, closes vim/vim#6764)
1b04ce2d40

Cherry-pick Test_glob() from patch 8.2.0634.

src/nvim/testdir/test_functions.vim

@@ -2015,6 +2015,25 @@ func Test_getmousepos()
   bwipe!
 endfunc
 
+" Test for glob()
+func Test_glob()
+  call assert_equal('', glob(v:_null_string))
+  call assert_equal('', globpath(v:_null_string, v:_null_string))
+
+  call writefile([], 'Xglob1')
+  call writefile([], 'XGLOB2')
+  set wildignorecase
+  " Sort output of glob() otherwise we end up with different
+  " ordering depending on whether file system is case-sensitive.
+  call assert_equal(['XGLOB2', 'Xglob1'], sort(glob('Xglob[12]', 0, 1)))
+  set wildignorecase&
+
+  call delete('Xglob1')
+  call delete('XGLOB2')
+
+  call assert_fails("call glob('*', 0, {})", 'E728:')
+endfunc
+
 func HasDefault(msg = 'msg')
   return a:msg
 endfunc