test: move runtime/autoload/* to provider/

- Organize tests by logical function, not the literal impl location.
- Avoid deep nesting / hyper-hierarchy.

test/functional/provider/python3_spec.lua

@@ -0,0 +1,77 @@
+do
+  local proc = io.popen(
+    [[python3 -c 'import neovim, sys; sys.stdout.write("ok")' 2> /dev/null]])
+  if proc:read() ~= 'ok' then
+    pending(
+      'python3 (or the python3 neovim module) is broken or missing',
+      function() end)
+    return
+  end
+end
+
+local helpers = require('test.functional.helpers')
+local eval, command, feed = helpers.eval, helpers.command, helpers.feed
+local eq, clear, insert = helpers.eq, helpers.clear, helpers.insert
+local expect, write_file = helpers.expect, helpers.write_file
+
+describe('python3 commands and functions', function()
+  before_each(function()
+    clear()
+    command('python3 import vim')
+  end)
+
+  it('feature test', function()
+    eq(1, eval('has("python3")'))
+  end)
+
+  it('python3_execute', function()
+    command('python3 vim.vars["set_by_python3"] = [100, 0]')
+    eq({100, 0}, eval('g:set_by_python3'))
+  end)
+
+  it('python3_execute with nested commands', function()
+    command([[python3 vim.command('python3 vim.command("python3 vim.command(\'let set_by_nested_python3 = 555\')")')]])
+    eq(555, eval('g:set_by_nested_python3'))
+  end)
+
+  it('python3_execute with range', function()
+    insert([[
+      line1
+      line2
+      line3
+      line4]])
+    feed('ggjvj:python3 vim.vars["range"] = vim.current.range[:]<CR>')
+    eq({'line2', 'line3'}, eval('g:range'))
+  end)
+
+  it('py3file', function()
+    local fname = 'py3file.py'
+    write_file(fname, 'vim.command("let set_by_py3file = 123")')
+    command('py3file py3file.py')
+    eq(123, eval('g:set_by_py3file'))
+    os.remove(fname)
+  end)
+
+  it('py3do', function()
+    -- :pydo3 42 returns None for all lines,
+    -- the buffer should not be changed
+    command('normal :py3do 42')
+    eq(0, eval('&mod'))
+    -- insert some text
+    insert('abc\ndef\nghi')
+    expect([[
+      abc
+      def
+      ghi]])
+    -- go to top and select and replace the first two lines
+    feed('ggvj:py3do return str(linenr)<CR>')
+    expect([[
+      1
+      2
+      ghi]])
+  end)
+
+  it('py3eval', function()
+    eq({1, 2, {['key'] = 'val'}}, eval([[py3eval('[1, 2, {"key": "val"}]')]]))
+  end)
+end)