patch 8.2.0243: insufficient code coverage for ex_docmd.c functions

Problem:    Insufficient code coverage for ex_docmd.c functions.
Solution:   Add more tests. (Yegappan Lakshmanan, closes #5618)

src/testdir/test_buffer.vim

@@ -0,0 +1,66 @@
+" Tests for Vim buffer
+
+" 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')
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab