tests: Migrate legacy test argument_0count.

src/nvim/testdir/Makefile

@@ -30,7 +30,6 @@ SCRIPTS := test_eval.out                                               \
            test_argument_count.out                                     \
            test_close_count.out                                        \
            test_command_count.out                                      \
-           test_argument_0count.out
 
 SCRIPTS_GUI := test16.out
 

src/nvim/testdir/test_argument_0count.in

@@ -1,28 +0,0 @@
-Tests for :0argadd and :0argedit     vim: set ft=vim :
-
-STARTTEST
-:so small.vim
-:let arglists = []
-:%argd
-:arga a b c d
-:2argu
-:0arga added
-:call add(arglists, argv())
-:2argu
-:arga third
-:call add(arglists, argv())
-:%argd
-:arga a b c d
-:2argu
-:0arge edited
-:call add(arglists, argv())
-:2argu
-:arga third
-:call add(arglists, argv())
-:e! test.out
-:call append(0, map(copy(arglists), 'join(v:val, " ")'))
-:w
-:qa!
-ENDTEST
-
-

src/nvim/testdir/test_argument_0count.ok

@@ -1,5 +0,0 @@
-added a b c d
-added a third b c d
-edited a b c d
-edited a third b c d
-

test/functional/legacy/argument_0count_spec.lua

@@ -0,0 +1,38 @@
+-- Tests for :0argadd and :0argedit
+
+local helpers = require('test.functional.helpers')
+local source, clear, expect = helpers.source, helpers.clear, helpers.expect
+
+describe('argument_0count', function()
+  setup(clear)
+
+  it('is working', function()
+    source([[
+      let arglists = []
+      arga a b c d
+      2argu
+      0arga added
+      call add(arglists, argv())
+      2argu
+      arga third
+      call add(arglists, argv())
+      %argd
+      arga a b c d
+      2argu
+      0arge edited
+      call add(arglists, argv())
+      2argu
+      arga third
+      call add(arglists, argv())
+      call append(0, map(copy(arglists), 'join(v:val, " ")'))
+    ]])
+
+    -- Assert buffer contents.
+    expect([=[
+      added a b c d
+      added a third b c d
+      edited a b c d
+      edited a third b c d
+      ]=])
+  end)
+end)