patch 8.2.2656: some command line arguments and regexp errors not tested

Problem:    Some command line arguments and regexp errors not tested.
Solution:   Add a few test cases. (Dominique Pellé, closes #8013)
diff --git a/src/testdir/test_startup.vim b/src/testdir/test_startup.vim
index 0817c9e..323b019 100644
--- a/src/testdir/test_startup.vim
+++ b/src/testdir/test_startup.vim
@@ -860,10 +860,12 @@
         \ 'Xtags')
   call writefile(['    first', '    second', '    third'], 'Xfile1')
 
-  if RunVim(before, after, '-t second')
-    call assert_equal(['Xfile1:L2C5'], readfile('Xtestout'))
-    call delete('Xtestout')
-  endif
+  for t_arg in ['-t second', '-tsecond']
+    if RunVim(before, after, '-t second')
+      call assert_equal(['Xfile1:L2C5'], readfile('Xtestout'), t_arg)
+      call delete('Xtestout')
+    endif
+  endfor
 
   call delete('Xtags')
   call delete('Xfile1')
@@ -1064,10 +1066,12 @@
 
   " A number argument sets the 'window' option
   call writefile(["iwindow \<C-R>=&window\<CR>\<Esc>:wq! Xresult\<CR>"], 'Xscriptin', 'b')
-  if RunVim([], [], '-s Xscriptin -w 17')
-    call assert_equal(["window 17"], readfile('Xresult'))
-    call delete('Xresult')
-  endif
+  for w_arg in ['-w 17', '-w17']
+    if RunVim([], [], '-s Xscriptin ' .. w_arg)
+      call assert_equal(["window 17"], readfile('Xresult'), w_arg)
+      call delete('Xresult')
+    endif
+  endfor
   call delete('Xscriptin')
 endfunc