test: add some tests with :normal and Ex mode

test/functional/ex_cmds/normal_spec.lua

@@ -1,7 +1,10 @@
 local helpers = require('test.functional.helpers')(after_each)
 local clear = helpers.clear
+local command = helpers.command
 local feed = helpers.feed
 local expect = helpers.expect
+local eq = helpers.eq
+local eval = helpers.eval
 
 before_each(clear)
 
@@ -10,4 +13,15 @@ describe(':normal', function()
     feed('gQnormal! Ifoo<CR>')
     expect('foo')
   end)
+
+  it('normal! does not execute command in Ex mode when running out of characters', function()
+    command('let g:var = 0')
+    command('normal! gQlet g:var = 1')
+    eq(0, eval('g:var'))
+  end)
+
+  it('normal! gQinsert does not hang #17980', function()
+    command('normal! gQinsert')
+    expect('')
+  end)
 end)