patch 8.1.0817: ":=" command is not tested

Problem:    ":=" command is not tested.
Solution:   Add a test. (Dominique Pelle, closes #3859)
diff --git a/src/testdir/test_alot.vim b/src/testdir/test_alot.vim
index be66512..81873af 100644
--- a/src/testdir/test_alot.vim
+++ b/src/testdir/test_alot.vim
@@ -10,6 +10,7 @@
 source test_compiler.vim
 source test_cursor_func.vim
 source test_delete.vim
+source test_ex_equal.vim
 source test_ex_undo.vim
 source test_ex_z.vim
 source test_execute_func.vim