test(pp): add macro expansion test

We don't actually do the full C expansion, as it can be seen by the
C-style comment character still present in the output, but it's better
than no expansion at all.

Author: gnikit

test/test_preproc_parser.py

@@ -21,3 +21,18 @@ def test_pp_leading_spaces():
         "FILE_ENCODING": ",encoding='UTF-8'",
     }
     assert defs == ref
+
+
+def test_pp_macro_expansion():
+    lines = [
+        "# define WRAP(PROCEDURE) PROCEDURE , wrap_/**/PROCEDURE",
+        "generic, public :: set => WRAP(abc)",
+        "procedure :: WRAP(abc)",
+    ]
+    ref = [
+        "# define WRAP(PROCEDURE) PROCEDURE , wrap_/**/PROCEDURE",
+        "generic, public :: set => abc , wrap_/**/abc",
+        "procedure :: abc , wrap_/**/abc",
+    ]
+    output, _, _, _ = preprocess_file(lines)
+    assert output == ref