patch 8.2.0023: command line editing not sufficiently tested

Problem:    Command line editing not sufficiently tested.
Solution:   Add more tests. (Dominique Pelle, closes #5374)
diff --git a/src/testdir/test_alot.vim b/src/testdir/test_alot.vim
index 894ec58..25241b2 100644
--- a/src/testdir/test_alot.vim
+++ b/src/testdir/test_alot.vim
@@ -13,6 +13,7 @@
 source test_ex_equal.vim
 source test_ex_undo.vim
 source test_ex_z.vim
+source test_ex_mode.vim
 source test_execute_func.vim
 source test_expand.vim
 source test_expand_dllpath.vim