scripts/sbom: add unit tests for SPDX-License-Identifier parsing

Verify that SPDX-License-Identifier headers at the top of source files
are parsed correctly.

Assisted-by: Cursor:claude-sonnet-4-5
Assisted-by: OpenCode:GLM-4-7
Co-developed-by: Maximilian Huber <maximilian.huber@tngtech.com>
Signed-off-by: Maximilian Huber <maximilian.huber@tngtech.com>
Signed-off-by: Luis Augenstein <luis.augenstein@tngtech.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

scripts/sbom/tests/spdx_graph/test_kernel_file.py

@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: GPL-2.0-only OR MIT
+# Copyright (C) 2025 TNG Technology Consulting GmbH
+
+import unittest
+from pathlib import Path
+import tempfile
+from sbom.spdx_graph.kernel_file import _parse_spdx_license_identifier  # type: ignore
+
+
+class TestKernelFile(unittest.TestCase):
+    def setUp(self):
+        self.tmpdir = tempfile.TemporaryDirectory()
+        self.src_tree = Path(self.tmpdir.name)
+
+    def tearDown(self):
+        self.tmpdir.cleanup()
+
+    def test_parse_spdx_license_identifier(self):
+        # REUSE-IgnoreStart
+        test_cases: list[tuple[str, str | None]] = [
+            ("/* SPDX-License-Identifier: MIT*/", "MIT"),
+            ("// SPDX-License-Identifier: GPL-2.0-only", "GPL-2.0-only"),
+            ("# SPDX-License-Identifier: GPL-2.0-only", "GPL-2.0-only"),
+            ("#!/bin/bash\n# SPDX-License-Identifier: GPL-2.0-only", "GPL-2.0-only"),
+            ("/* SPDX-License-Identifier: GPL-2.0-or-later OR MIT */", "GPL-2.0-or-later OR MIT"),
+            ("/* SPDX-License-Identifier: Apache-2.0 */\n extra text", "Apache-2.0"),
+            ("<!-- SPDX-License-Identifier: GPL-2.0 -->", "GPL-2.0"),
+            ("int main() { return 0; }", None),
+        ]
+        # REUSE-IgnoreEnd
+
+        for i, (file_content, expected_identifier) in enumerate(test_cases):
+            file_path = self.src_tree / f"file_{i}.c"
+            file_path.write_text(file_content)
+            self.assertEqual(_parse_spdx_license_identifier(str(file_path)), expected_identifier)