Add regression test for backslash-newline at EOF

gcc accepts this with a warning and clang accepts it silently, but CBI exits
with a RuntimeError.

Signed-off-by: John Pennycook <[email protected]>

Author: Pennycook

tests/preprocessor/__init__.py

@@ -0,0 +1,2 @@
+# Copyright (C) 2019 Intel Corporation
+# SPDX-License-Identifier: BSD-3-Clause

tests/preprocessor/test_warnings.py

@@ -0,0 +1,42 @@
+# Copyright (C) 2019-2024 Intel Corporation
+# SPDX-License-Identifier: BSD-3-Clause
+
+import logging
+import os
+import tempfile
+import unittest
+from pathlib import Path
+
+from codebasin import file_parser
+
+
+class TestPreprocessorWarnings(unittest.TestCase):
+    """
+    Test that preprocessor generates warnings for weird corner cases.
+    """
+
+    def setUp(self):
+        self.cwd = os.getcwd()
+
+    def tearDown(self):
+        os.chdir(self.cwd)
+
+    def test_backslash_eof(self):
+        """Check backslash-newline at EOF is only a warning"""
+        tmp = tempfile.TemporaryDirectory()
+        path = Path(tmp.name)
+        os.chdir(tmp.name)
+
+        with open(path / "test.hpp", mode="w") as f:
+            f.write("#define BAD_MACRO \\\n")
+
+        parser = file_parser.FileParser(path / "test.hpp")
+
+        logging.disable(logging.NOTSET)
+        logger = logging.getLogger("codebasin")
+        with self.assertLogs(logger, level="WARNING") as cm:
+            _ = parser.parse_file()
+        logging.disable()
+        self.assertRegex(cm.output[0], "backslash-newline at end of file")
+
+        tmp.cleanup()