test: check enabled_if and tests stanza alias interaction

Signed-off-by: Ali Caglayan <alizter@gmail.com>

Author: Alizter

test/blackbox-tests/test-cases/stanzas/tests/tests-stanza-alias.t

@@ -20,3 +20,19 @@ Tests stanzas produce aliases with the executable names
   $ dune build @a @b
   a
   b
+
+Checking interaction with enabled_if
+
+  $ cat > dune << EOF
+  > (tests
+  >  (names a b)
+  >  (enabled_if false))
+  > EOF
+
+  $ dune build @a @b
+  Error: Alias "a" specified on the command line is empty.
+  It is not defined in . or any of its descendants.
+  Hint: did you mean all?
+  Error: Alias "b" specified on the command line is empty.
+  It is not defined in . or any of its descendants.
+  [1]