Closes #3 Validate DBC frame definitions and report error locations

tests/README.md

@@ -26,3 +26,22 @@ signals, signed values, scaling, 64-bit extraction, signed/unsigned boundary val
 (including `INT64_MIN`, `INT64_MAX`, and `UINT64_MAX`), numeric output, invalid lengths, insufficient
 payloads, and Intel regression cases. Frame validity means the definition was
 found; insufficient payloads are checked through signal validity.
+
+## Parser regression tests
+
+Run from the repository root:
+
+```sh
+g++ -std=c++17 -Wall -Wextra -Wpedantic -Werror -I. \
+  tests/dbc_parser_test.cpp dbc_parser.cpp -o /tmp/dbc_parser_test
+/tmp/dbc_parser_test
+```
+
+For qmake, use `tests/dbc_parser_test.pro` in a separate build directory,
+following the decoder instructions above, then run `./dbc_parser_test`.
+
+Parser tests cover standard and extended CAN IDs, whitespace, payload storage
+boundaries, missing fields, malformed and overflowing numbers, reserved ID bits,
+error paths and line numbers, and integration with signals and comments.
+Temporary DBC fixtures are created in the system temporary directory and removed
+automatically.