diff --git a/test/functional/helpers.lua b/test/functional/helpers.lua
index 92c83b5f49..4dde733e1e 100644
--- a/test/functional/helpers.lua
+++ b/test/functional/helpers.lua
@@ -419,6 +419,14 @@ end
 --    clear('-e')
 --    clear{args={'-e'}, args_rm={'-i'}, env={TERM=term}}
 function module.clear(...)
+  local argv, env = module.new_argv(...)
+  module.set_session(module.spawn(argv, nil, env))
+end
+
+-- Builds an argument list for use in clear().
+--
+--@see clear() for parameters.
+function module.new_argv(...)
   local args = {unpack(module.nvim_argv)}
   table.insert(args, '--headless')
   local new_args
@@ -458,7 +466,7 @@ function module.clear(...)
   for _, arg in ipairs(new_args) do
     table.insert(args, arg)
   end
-  module.set_session(module.spawn(args, nil, env))
+  return args, env
 end
 
 function module.insert(...)
diff --git a/test/functional/shada/buffers_spec.lua b/test/functional/shada/buffers_spec.lua
index a4746c2205..04c9c01d7c 100644
--- a/test/functional/shada/buffers_spec.lua
+++ b/test/functional/shada/buffers_spec.lua
@@ -1,26 +1,22 @@
--- ShaDa buffer list saving/reading support
+-- shada buffer list saving/reading support
 local helpers = require('test.functional.helpers')(after_each)
 local nvim_command, funcs, eq, curbufmeths =
   helpers.command, helpers.funcs, helpers.eq, helpers.curbufmeths
 
 local shada_helpers = require('test.functional.shada.helpers')
-local reset, set_additional_cmd, clear =
-  shada_helpers.reset, shada_helpers.set_additional_cmd,
-  shada_helpers.clear
+local reset, clear = shada_helpers.reset, shada_helpers.clear
 
-describe('ShaDa support code', function()
+describe('shada support code', function()
   local testfilename = 'Xtestfile-functional-shada-buffers'
   local testfilename_2 = 'Xtestfile-functional-shada-buffers-2'
-  before_each(reset)
   after_each(clear)
 
   it('is able to dump and restore buffer list', function()
-    set_additional_cmd('set shada+=%')
-    reset()
+    reset('set shada+=%')
     nvim_command('edit ' .. testfilename)
     nvim_command('edit ' .. testfilename_2)
     nvim_command('qall')
-    reset()
+    reset('set shada+=%')
     eq(3, funcs.bufnr('$'))
     eq('', funcs.bufname(1))
     eq(testfilename, funcs.bufname(2))
@@ -28,11 +24,9 @@ describe('ShaDa support code', function()
   end)
 
   it('does not restore buffer list without % in &shada', function()
-    set_additional_cmd('set shada+=%')
-    reset()
+    reset('set shada+=%')
     nvim_command('edit ' .. testfilename)
     nvim_command('edit ' .. testfilename_2)
-    set_additional_cmd('')
     nvim_command('qall')
     reset()
     eq(1, funcs.bufnr('$'))
@@ -40,61 +34,57 @@ describe('ShaDa support code', function()
   end)
 
   it('does not dump buffer list without % in &shada', function()
+    reset()
     nvim_command('edit ' .. testfilename)
     nvim_command('edit ' .. testfilename_2)
-    set_additional_cmd('set shada+=%')
     nvim_command('qall')
-    reset()
+    reset('set shada+=%')
     eq(1, funcs.bufnr('$'))
     eq('', funcs.bufname(1))
   end)
 
   it('does not dump unlisted buffer', function()
-    set_additional_cmd('set shada+=%')
-    reset()
+    reset('set shada+=%')
     nvim_command('edit ' .. testfilename)
     nvim_command('edit ' .. testfilename_2)
     curbufmeths.set_option('buflisted', false)
     nvim_command('qall')
-    reset()
+    reset('set shada+=%')
     eq(2, funcs.bufnr('$'))
     eq('', funcs.bufname(1))
     eq(testfilename, funcs.bufname(2))
   end)
 
   it('does not dump quickfix buffer', function()
-    set_additional_cmd('set shada+=%')
-    reset()
+    reset('set shada+=%')
     nvim_command('edit ' .. testfilename)
     nvim_command('edit ' .. testfilename_2)
     curbufmeths.set_option('buftype', 'quickfix')
     nvim_command('qall')
-    reset()
+    reset('set shada+=%')
     eq(2, funcs.bufnr('$'))
     eq('', funcs.bufname(1))
     eq(testfilename, funcs.bufname(2))
   end)
 
   it('does not dump unnamed buffers', function()
-    set_additional_cmd('set shada+=% hidden')
-    reset()
+    reset('set shada+=% hidden')
     curbufmeths.set_lines(0, 1, true, {'foo'})
     nvim_command('enew')
     curbufmeths.set_lines(0, 1, true, {'bar'})
     eq(2, funcs.bufnr('$'))
     nvim_command('qall!')
-    reset()
+    reset('set shada+=% hidden')
     eq(1, funcs.bufnr('$'))
     eq('', funcs.bufname(1))
   end)
 
   it('restores 1 buffer with %1 in &shada, #5759', function()
-    set_additional_cmd('set shada+=%1')
-    reset()
+    reset('set shada+=%1')
     nvim_command('edit ' .. testfilename)
     nvim_command('edit ' .. testfilename_2)
     nvim_command('qall')
-    reset()
+    reset('set shada+=%1')
     eq(2, funcs.bufnr('$'))
     eq('', funcs.bufname(1))
     eq(testfilename, funcs.bufname(2))
diff --git a/test/functional/shada/helpers.lua b/test/functional/shada/helpers.lua
index d5e061bb50..fb3ec4a87c 100644
--- a/test/functional/shada/helpers.lua
+++ b/test/functional/shada/helpers.lua
@@ -1,47 +1,39 @@
 local helpers = require('test.functional.helpers')(nil)
-local spawn, set_session, meths, nvim_prog =
-  helpers.spawn, helpers.set_session, helpers.meths, helpers.nvim_prog
-local write_file, merge_args = helpers.write_file, helpers.merge_args
+local meths = helpers.meths
+local write_file = helpers.write_file
+local concat_tables = helpers.concat_tables
 
 local mpack = require('mpack')
 
 local tmpname = helpers.tmpname()
-local append_argv = nil
 
-local function nvim_argv(shada_file, embed)
-  if embed == nil then
-    embed = true
+--   o={
+--     args=…,
+--     args_rm=…,
+--     shadafile=…,
+--   }
+local function reset(o)
+  assert(o == nil or type(o) == 'table' or type(o) == 'string')
+  o = o and o or {}
+  local args_rm = o.args_rm or {}
+  table.insert(args_rm, '-i')
+  local args={
+    '-i', o.shadafile or tmpname,
+  }
+  if type(o) == 'string' then
+    args = concat_tables(args, {'--cmd', o})
+  elseif o.args then
+    args = concat_tables(args, o.args)
   end
-  local argv = {nvim_prog, '-u', 'NONE', '-i', shada_file or tmpname, '-N',
-                '--cmd', 'set shortmess+=I background=light noswapfile',
-                '--headless', embed  and '--embed' or nil}
-  if helpers.prepend_argv or append_argv then
-    return merge_args(helpers.prepend_argv, argv, append_argv)
-  else
-    return argv
-  end
-end
-
-local reset = function(shada_file)
-  set_session(spawn(nvim_argv(shada_file)))
+  helpers.clear{
+    args_rm=args_rm,
+    args=args,
+  }
   meths.set_var('tmpname', tmpname)
 end
 
-local set_additional_cmd = function(s)
-  append_argv = {'--cmd', s}
-end
-
-local function add_argv(...)
-  if select('#', ...) == 0 then
-    append_argv = nil
-  else
-    append_argv = {...}
-  end
-end
-
 local clear = function()
   os.remove(tmpname)
-  append_argv = nil
 end
 
 local get_shada_rw = function(fname)
@@ -89,10 +81,7 @@ end
 
 return {
   reset=reset,
-  set_additional_cmd=set_additional_cmd,
-  add_argv=add_argv,
   clear=clear,
   get_shada_rw=get_shada_rw,
   read_shada_file=read_shada_file,
-  nvim_argv=nvim_argv,
 }
diff --git a/test/functional/shada/marks_spec.lua b/test/functional/shada/marks_spec.lua
index e6450e68b3..e319fd9e6b 100644
--- a/test/functional/shada/marks_spec.lua
+++ b/test/functional/shada/marks_spec.lua
@@ -6,11 +6,7 @@ local meths, curwinmeths, curbufmeths, nvim_command, funcs, eq =
 local exc_exec, redir_exec = helpers.exc_exec, helpers.redir_exec
 
 local shada_helpers = require('test.functional.shada.helpers')
-local reset, set_additional_cmd, clear =
-  shada_helpers.reset, shada_helpers.set_additional_cmd,
-  shada_helpers.clear
-local add_argv = shada_helpers.add_argv
-local nvim_argv = shada_helpers.nvim_argv
+local reset, clear = shada_helpers.reset, shada_helpers.clear
 
 local nvim_current_line = function()
   return curwinmeths.get_cursor()[1]
@@ -71,8 +67,7 @@ describe('ShaDa support code', function()
     nvim_command('2')
     nvim_command('kB')
     nvim_command('wshada')
-    set_additional_cmd('set shada=\'0,f0')
-    reset()
+    reset('set shada=\'0,f0')
     nvim_command('language C')
     nvim_command('normal! `A')
     eq(testfilename, funcs.fnamemodify(curbufmeths.get_name(), ':t'))
@@ -223,17 +218,32 @@ describe('ShaDa support code', function()
   -- during -c used to add item with zero lnum to jump list.
   it('does not create incorrect file for non-existent buffers when writing from -c',
   function()
-    add_argv('--cmd', 'silent edit ' .. non_existent_testfilename, '-c', 'qall')
-    local argv = nvim_argv(nil, false) -- no --embed
+    local argv = helpers.new_argv{
+      args_rm={
+        '-i',
+        '--embed',  -- no --embed
+      },
+      args={
+        '-i', meths.get_var('tmpname'),  -- Use same shada file as parent.
+        '--cmd', 'silent edit '..non_existent_testfilename,
+        '-c', 'qall'},
+    }
     eq('', funcs.system(argv))
     eq(0, exc_exec('rshada'))
   end)
 
   it('does not create incorrect file for non-existent buffers opened from -c',
   function()
-    add_argv('-c', 'silent edit ' .. non_existent_testfilename,
-             '-c', 'autocmd VimEnter * qall')
-    local argv = nvim_argv(nil, false) -- no --embed
+    local argv = helpers.new_argv{
+      args_rm={
+        '-i',
+        '--embed',  -- no --embed
+      },
+      args={
+        '-i', meths.get_var('tmpname'),  -- Use same shada file as parent.
+        '-c', 'silent edit '..non_existent_testfilename,
+        '-c', 'autocmd VimEnter * qall'},
+    }
     eq('', funcs.system(argv))
     eq(0, exc_exec('rshada'))
   end)
diff --git a/test/functional/shada/registers_spec.lua b/test/functional/shada/registers_spec.lua
index 71af14aba8..1f06cbe350 100644
--- a/test/functional/shada/registers_spec.lua
+++ b/test/functional/shada/registers_spec.lua
@@ -3,9 +3,7 @@ local helpers = require('test.functional.helpers')(after_each)
 local nvim_command, funcs, eq = helpers.command, helpers.funcs, helpers.eq
 
 local shada_helpers = require('test.functional.shada.helpers')
-local reset, set_additional_cmd, clear =
-  shada_helpers.reset, shada_helpers.set_additional_cmd,
-  shada_helpers.clear
+local reset, clear = shada_helpers.reset, shada_helpers.clear
 
 local setreg = function(name, contents, typ)
   if type(contents) == 'string' then
@@ -52,9 +50,8 @@ describe('ShaDa support code', function()
     setreg('c', {'d', 'e', ''}, 'c')
     setreg('l', {'a', 'b', 'cde'}, 'l')
     setreg('b', {'bca', 'abc', 'cba'}, 'b3')
-    set_additional_cmd('set shada=\'0,<0')
     nvim_command('qall')
-    reset()
+    reset('set shada=\'0,<0')
     eq({{'d', 'e', ''}, 'v'}, getreg('c'))
     eq({{'a', 'b', 'cde'}, 'V'}, getreg('l'))
     eq({{'bca', 'abc', 'cba'}, '\0223'}, getreg('b'))
@@ -76,9 +73,8 @@ describe('ShaDa support code', function()
     setreg('c', {'d', 'e', ''}, 'c')
     setreg('l', {'a', 'b', 'cde'}, 'l')
     setreg('b', {'bca', 'abc', 'cba'}, 'b3')
-    set_additional_cmd('set shada=\'0,\\"0')
     nvim_command('qall')
-    reset()
+    reset('set shada=\'0,\\"0')
     eq({{'d', 'e', ''}, 'v'}, getreg('c'))
     eq({{'a', 'b', 'cde'}, 'V'}, getreg('l'))
     eq({{'bca', 'abc', 'cba'}, '\0223'}, getreg('b'))
@@ -142,7 +138,6 @@ describe('ShaDa support code', function()
     reset()
     -- \171 is U+00AB LEFT-POINTING DOUBLE ANGLE QUOTATION MARK in latin1
     setreg('e', {'\171«'}, 'c')
-    set_additional_cmd('')
     nvim_command('qall')
     reset()
     eq({{'\171«'}, 'v'}, getreg('e'))
diff --git a/test/functional/shada/shada_spec.lua b/test/functional/shada/shada_spec.lua
index 5f7daf73e5..ff63aed235 100644
--- a/test/functional/shada/shada_spec.lua
+++ b/test/functional/shada/shada_spec.lua
@@ -15,7 +15,6 @@ local shada_helpers = require('test.functional.shada.helpers')
 local reset, clear, get_shada_rw =
   shada_helpers.reset, shada_helpers.clear, shada_helpers.get_shada_rw
 local read_shada_file = shada_helpers.read_shada_file
-local set_additional_cmd = shada_helpers.set_additional_cmd
 
 local wshada, _, shada_fname, clean =
   get_shada_rw('Xtest-functional-shada-shada.shada')
@@ -244,8 +243,7 @@ describe('ShaDa support code', function()
 
     funcs.mkdir(dirname, '', 0)
     eq(0, funcs.filewritable(dirname))
-    set_additional_cmd('set shada=')
-    reset(dirshada)
+    reset{shadafile=dirshada, args={'--cmd', 'set shada='}}
     meths.set_option('shada', '\'10')
     eq('Vim(wshada):E886: System error while opening ShaDa file '
        .. 'Xtest-functional-shada-shada.d/main.shada for reading to merge '
diff --git a/test/functional/shada/variables_spec.lua b/test/functional/shada/variables_spec.lua
index f817bcef74..74bbceddcc 100644
--- a/test/functional/shada/variables_spec.lua
+++ b/test/functional/shada/variables_spec.lua
@@ -4,9 +4,7 @@ local meths, funcs, nvim_command, eq, exc_exec =
   helpers.meths, helpers.funcs, helpers.command, helpers.eq, helpers.exc_exec
 
 local shada_helpers = require('test.functional.shada.helpers')
-local reset, set_additional_cmd, clear =
-  shada_helpers.reset, shada_helpers.set_additional_cmd,
-  shada_helpers.clear
+local reset, clear = shada_helpers.reset, shada_helpers.clear
 
 describe('ShaDa support code', function()
   before_each(reset)
@@ -25,8 +23,7 @@ describe('ShaDa support code', function()
   local autotest = function(tname, varname, varval, val_is_expr)
     it('is able to dump and read back ' .. tname .. ' variable automatically',
     function()
-      set_additional_cmd('set shada+=!')
-      reset()
+      reset('set shada+=!')
       if val_is_expr then
         nvim_command('let g:' .. varname .. ' = ' .. varval)
         varval = meths.get_var(varname)
@@ -36,7 +33,7 @@ describe('ShaDa support code', function()
       -- Exit during `reset` is not a regular exit: it does not write shada
       -- automatically
       nvim_command('qall')
-      reset()
+      reset('set shada+=!')
       eq(varval, meths.get_var(varname))
     end)
   end
@@ -55,8 +52,7 @@ describe('ShaDa support code', function()
     meths.set_var('STRVAR', 'foo')
     nvim_command('set shada+=!')
     nvim_command('wshada')
-    set_additional_cmd('set shada-=!')
-    reset()
+    reset('set shada-=!')
     nvim_command('rshada')
     eq(0, funcs.exists('g:STRVAR'))
   end)
@@ -98,7 +94,6 @@ describe('ShaDa support code', function()
     meths.set_var('LSTVAR', {'«'})
     meths.set_var('DCTVAR', {['«']='«'})
     meths.set_var('NESTEDVAR', {['«']={{'«'}, {['«']='«'}, {a='Test'}}})
-    set_additional_cmd('')
     nvim_command('qall')
     reset()
     eq('«', meths.get_var('STRVAR'))
@@ -131,11 +126,10 @@ describe('ShaDa support code', function()
     nvim_command('let F = function("tr")')
     meths.set_var('U', '10')
     nvim_command('set shada+=!')
-    set_additional_cmd('set shada+=!')
     eq('Vim(wshada):E5004: Error while dumping variable g:F, itself: attempt to dump function reference',
        exc_exec('wshada'))
     meths.set_option('shada', '')
-    reset()
+    reset('set shada+=!')
     eq('10', meths.get_var('U'))
   end)
 
@@ -148,8 +142,7 @@ describe('ShaDa support code', function()
     eq('Vim(wshada):E5005: Unable to dump variable g:L: container references itself in index 0',
        exc_exec('wshada'))
     meths.set_option('shada', '')
-    set_additional_cmd('set shada+=!')
-    reset()
+    reset('set shada+=!')
     eq('10', meths.get_var('U'))
   end)
 end)