tests: Migrate legacy test 8. #4179

The test produces some "hit enter" prompts and error messages that had to be
dealt with by `feed`ing CTRL-L to nvim.

src/nvim/testdir/Makefile

@@ -8,7 +8,6 @@ VIMPROG := ../../../build/bin/nvim
 SCRIPTSOURCE := ../../../runtime
 
 SCRIPTS := \
-           test8.out              \
            test13.out             \
            test14.out             \
            test17.out             \

src/nvim/testdir/test8.in

@@ -1,43 +0,0 @@
-Test for BufWritePre autocommand that deletes or unloads the buffer.
-Test for BufUnload autocommand that unloads all other buffers.
-
-STARTTEST
-:au BufWritePre Xxx1 bunload
-:au BufWritePre Xxx2 bwipe
-/^start of
-A1:.,/end of/w! Xxx1  " write test file Xxx1
-$r2:.,/end of/w! Xxx2   " write test file Xxx2
-:e! Xxx2                " edit Xxx2
-:bdel test8.in		" delete this file from the buffer list
-:e Xxx1                 " edit Xxx1
-:w                      " write it, will unload it and give an error msg
-:w! test.out            " Write contents of this file
-:e! Xxx2                " start editing Xxx2
-:bwipe test.out         " remove test.out from the buffer list
-:w                      " write it, will delete the buffer and give an error msg
-:w >>test.out           " Append contents of this file
-:au! BufWritePre
-:func CloseAll()
-  let i = 0
-  while i <= bufnr('$')
-    if i != bufnr('%') && bufloaded(i)
-      exe  i . "bunload"
-    endif
-    let i += 1
-  endwhile
-endfunc
-:func WriteToOut()
-  edit! test.out
-  $put ='VimLeave done'
-  write
-endfunc
-:set shada='100
-:au BufUnload * call CloseAll()
-:au VimLeave * call WriteToOut()
-:q
-:qa!
-ENDTEST
-
-start of Xxx
-	test
-end of Xxx

src/nvim/testdir/test8.ok

@@ -1,7 +0,0 @@
-start of Xxx2
-	test
-end of Xxx
-start of Xxx1
-	test
-end of Xxx
-VimLeave done

test/functional/legacy/008_autocommands_spec.lua

@@ -0,0 +1,90 @@
+-- Test for BufWritePre autocommand that deletes or unloads the buffer.
+-- Test for BufUnload autocommand that unloads all other buffers.
+
+local helpers = require('test.functional.helpers')(after_each)
+local feed, source = helpers.feed, helpers.source
+local clear, execute, expect, eq, eval = helpers.clear, helpers.execute, helpers.expect, helpers.eq, helpers.eval
+local write_file, wait, dedent = helpers.write_file, helpers.wait, helpers.dedent
+local io = require('io')
+
+describe('autocommands that delete and unload buffers:', function()
+  local text1 = dedent([[
+    start of Xxx1
+      test
+    end of Xxx]])
+  local text2 = text1:gsub('1', '2')
+  setup(function()
+    write_file('Xxx1', text1..'\n')
+    write_file('Xxx2', text2..'\n')
+  end)
+  teardown(function()
+    os.remove('test.out')
+    os.remove('Xxx1')
+    os.remove('Xxx2')
+  end)
+  before_each(clear)
+
+  it('BufWritePre, BufUnload', function()
+    execute('au BufWritePre Xxx1 bunload')
+    execute('au BufWritePre Xxx2 bwipe')
+    execute('e Xxx2')
+    eq('Xxx2', eval('bufname("%")'))
+    execute('e Xxx1')
+    eq('Xxx1', eval('bufname("%")'))
+    -- The legacy test file did not check the error message.
+    execute('let v:errmsg = "no error"')
+    execute('write')
+    -- Discard all "hit enter" prompts and messages.
+    feed('<C-L>')
+    eq('E203: Autocommands deleted or unloaded buffer to be written',
+      eval('v:errmsg'))
+    eq('Xxx2', eval('bufname("%")'))
+    expect(text2)
+    -- Start editing Xxx2.
+    execute('e! Xxx2')
+    -- The legacy test file did not check the error message.
+    execute('let v:errmsg = "no error"')
+    -- Write Xxx2, will delete the buffer and give an error msg.
+    execute('w')
+    -- Discard all "hit enter" prompts and messages.
+    feed('<C-L>')
+    eq('E203: Autocommands deleted or unloaded buffer to be written',
+      eval('v:errmsg'))
+    eq('Xxx1', eval('bufname("%")'))
+    expect(text1)
+  end)
+  it('BufUnload, VimLeave', function()
+    source([[
+      func CloseAll()
+	let i = 0
+	while i <= bufnr('$')
+	  if i != bufnr('%') && bufloaded(i)
+	    exe  i . "bunload"
+	  endif
+	  let i += 1
+	endwhile
+      endfunc
+      func WriteToOut()
+	edit! test.out
+	$put ='VimLeave done'
+	write
+      endfunc
+      set shada='100
+      au BufUnload * call CloseAll()
+      au VimLeave * call WriteToOut()
+    ]])
+    execute('e Xxx2')
+    -- Discard all "hit enter" prompts and messages.
+    feed('<C-L>')
+    execute('e Xxx1')
+    -- Discard all "hit enter" prompts and messages.
+    feed('<C-L>')
+    execute('e Makefile') -- an existing file
+    feed('<C-L>')
+    execute('sp new2')
+    feed('<C-L>')
+    execute('q')
+    wait()
+    eq('\nVimLeave done\n', io.open('test.out', 'r'):read('*all'))
+  end)
+end)