vim-patch:8.2.0261: some code not covered by tests

Problem:    Some code not covered by tests.
Solution:   Add test cases. (Yegappan Lakshmanan, closes vim/vim#5645)
f0cee1971f

Cherry-pick Test_bunload_with_offset() from patch 8.2.0243

src/nvim/testdir/test_buffer.vim

@@ -2,6 +2,160 @@
 
 source check.vim
 
+" Test for the :bunload command with an offset
+func Test_bunload_with_offset()
+  %bwipe!
+  call writefile(['B1'], 'b1')
+  call writefile(['B2'], 'b2')
+  call writefile(['B3'], 'b3')
+  call writefile(['B4'], 'b4')
+
+  " Load four buffers. Unload the second and third buffers and then
+  " execute .+3bunload to unload the last buffer.
+  edit b1
+  new b2
+  new b3
+  new b4
+
+  bunload b2
+  bunload b3
+  exe bufwinnr('b1') . 'wincmd w'
+  .+3bunload
+  call assert_equal(0, getbufinfo('b4')[0].loaded)
+  call assert_equal('b1',
+        \ fnamemodify(getbufinfo({'bufloaded' : 1})[0].name, ':t'))
+
+  " Load four buffers. Unload the third and fourth buffers. Execute .+3bunload
+  " and check whether the second buffer is unloaded.
+  ball
+  bunload b3
+  bunload b4
+  exe bufwinnr('b1') . 'wincmd w'
+  .+3bunload
+  call assert_equal(0, getbufinfo('b2')[0].loaded)
+  call assert_equal('b1',
+        \ fnamemodify(getbufinfo({'bufloaded' : 1})[0].name, ':t'))
+
+  " Load four buffers. Unload the second and third buffers and from the last
+  " buffer execute .-3bunload to unload the first buffer.
+  ball
+  bunload b2
+  bunload b3
+  exe bufwinnr('b4') . 'wincmd w'
+  .-3bunload
+  call assert_equal(0, getbufinfo('b1')[0].loaded)
+  call assert_equal('b4',
+        \ fnamemodify(getbufinfo({'bufloaded' : 1})[0].name, ':t'))
+
+  " Load four buffers. Unload the first and second buffers. Execute .-3bunload
+  " from the last buffer and check whether the third buffer is unloaded.
+  ball
+  bunload b1
+  bunload b2
+  exe bufwinnr('b4') . 'wincmd w'
+  .-3bunload
+  call assert_equal(0, getbufinfo('b3')[0].loaded)
+  call assert_equal('b4',
+        \ fnamemodify(getbufinfo({'bufloaded' : 1})[0].name, ':t'))
+
+  %bwipe!
+  call delete('b1')
+  call delete('b2')
+  call delete('b3')
+  call delete('b4')
+
+  call assert_fails('1,4bunload', 'E16:')
+  call assert_fails(',100bunload', 'E16:')
+
+  " Use a try-catch for this test. When assert_fails() is used for this
+  " test, the command fails with E515: instead of E90:
+  let caught_E90 = 0
+  try
+    $bunload
+  catch /E90:/
+    let caught_E90 = 1
+  endtry
+  call assert_equal(1, caught_E90)
+  call assert_fails('$bunload', 'E515:')
+endfunc
+
+" Test for :buffer, :bnext, :bprevious, :brewind, :blast and :bmodified
+" commands
+func Test_buflist_browse()
+  %bwipe!
+  call assert_fails('buffer 1000', 'E86:')
+
+  call writefile(['foo1', 'foo2', 'foo3', 'foo4'], 'Xfile1')
+  call writefile(['bar1', 'bar2', 'bar3', 'bar4'], 'Xfile2')
+  call writefile(['baz1', 'baz2', 'baz3', 'baz4'], 'Xfile3')
+  edit Xfile1
+  let b1 = bufnr()
+  edit Xfile2
+  let b2 = bufnr()
+  edit +/baz4 Xfile3
+  let b3 = bufnr()
+
+  call assert_fails('buffer ' .. b1 .. ' abc', 'E488:')
+  call assert_equal(b3, bufnr())
+  call assert_equal(4, line('.'))
+  exe 'buffer +/bar2 ' .. b2
+  call assert_equal(b2, bufnr())
+  call assert_equal(2, line('.'))
+  exe 'buffer +/bar1'
+  call assert_equal(b2, bufnr())
+  call assert_equal(1, line('.'))
+
+  brewind +/foo3
+  call assert_equal(b1, bufnr())
+  call assert_equal(3, line('.'))
+
+  blast +/baz2
+  call assert_equal(b3, bufnr())
+  call assert_equal(2, line('.'))
+
+  bprevious +/bar4
+  call assert_equal(b2, bufnr())
+  call assert_equal(4, line('.'))
+
+  bnext +/baz3
+  call assert_equal(b3, bufnr())
+  call assert_equal(3, line('.'))
+
+  call assert_fails('bmodified', 'E84:')
+  call setbufvar(b2, '&modified', 1)
+  exe 'bmodified +/bar3'
+  call assert_equal(b2, bufnr())
+  call assert_equal(3, line('.'))
+
+  " With no listed buffers in the list, :bnext and :bprev should fail
+  %bwipe!
+  set nobuflisted
+  call assert_fails('bnext', 'E85:')
+  call assert_fails('bprev', 'E85:')
+  set buflisted
+
+  call assert_fails('sandbox bnext', 'E48:')
+
+  call delete('Xfile1')
+  call delete('Xfile2')
+  call delete('Xfile3')
+  %bwipe!
+endfunc
+
+" Test for :bdelete
+func Test_bdelete_cmd()
+  %bwipe!
+  call assert_fails('bdelete 5', 'E516:')
+
+  " Deleting a unlisted and unloaded buffer
+  edit Xfile1
+  let bnr = bufnr()
+  set nobuflisted
+  enew
+  call assert_fails('bdelete ' .. bnr, 'E516:')
+  %bwipe!
+endfunc
+
 func Test_buffer_error()
   new foo1
   new foo2