legacy tests: migrate test20

src/nvim/testdir/test20.in

@@ -1,28 +0,0 @@
-Tests Blockwise Visual when there are TABs before the text.
-First test for undo working properly when executing commands from a register.
-Also test this in an empty buffer.
-
-STARTTEST
-:so tiny.vim
-G0"ay$k@au
-:new
-@auY:quit!
-GP
-/start here$
-"by$jjlld
-/456$
-jj"bP
-:/56$/,$-1w! test.out
-:qa!
-ENDTEST
-
-123456
-234567
-345678
-
-test text test tex start here
-		some text
-		test text
-test text
-
-OxjAykdd

src/nvim/testdir/test20.ok

@@ -1,10 +0,0 @@
-123start here56
-234start here67
-345start here78
-
-test text test tex rt here
-		somext
-		tesext
-test text
-
-

test/functional/legacy/020_blockwise_visual_spec.lua

@@ -0,0 +1,49 @@
+-- vim: set foldmethod=marker foldmarker=[[,]] :
+-- Tests Blockwise Visual when there are TABs before the text.
+-- First test for undo working properly when executing commands from a register.
+-- Also test this in an empty buffer.
+
+local helpers = require('test.functional.helpers')
+local clear, feed, insert = helpers.clear, helpers.feed, helpers.insert
+local execute, expect = helpers.execute, helpers.expect
+
+describe('blockwise visual', function()
+  setup(clear)
+
+  it('is working', function()
+    insert([[
+123456
+234567
+345678
+
+test text test tex start here
+		some text
+		test text
+test text
+
+x	jAy kdd
+Ox jAy kdd]])
+
+    feed(":let @a = 'Ox<C-v><Esc>jAy<C-v><Esc>kdd'<cr>")
+    feed('G0k@au')
+    execute('new')
+    feed('@auY')
+    execute('quit')
+    feed('GP')
+    execute('/start here')
+    feed('"by$<C-v>jjlld')
+    execute('/456')
+    feed('<C-v>jj"bP')
+    execute('$-3,$d')
+
+    expect([[
+123start here56
+234start here67
+345start here78
+
+test text test tex rt here
+		somext
+		tesext
+test text]])
+  end)
+end)