Closes #11

tests/README.md

@@ -1,25 +1,40 @@
-# Decoder regression tests
+# QtTest regression tests
 
-Run from the repository root with a C++17 compiler:
+Open the repository's root `dbc.pro` in Qt Creator. It contains `core` (a static
+C++17 library) and `tests` (the `dbc_tests` QtTest executable). Core is built first;
+tests link its archive rather than compiling its implementation again.
+Qt Core and Qt Test development packages are required for tests only.
+
+Build from the repository root with Qt 6 (use `qmake` for Qt 5):
 
 ```sh
-g++ -std=c++17 -Wall -Wextra -Wpedantic -I. \
-  tests/dbc_decoder_test.cpp dbc_decoder.cpp -o /tmp/dbc_decoder_test
-/tmp/dbc_decoder_test
+mkdir build
+cd build
+qmake6 ../dbc.pro
+make -j
+make check
 ```
 
-Alternatively, build the standalone qmake project out of source:
+Or run `./tests/dbc_tests` directly. Both parser and decoder suites run, and the
+executable returns nonzero when either suite fails. Decoder cases appear as
+individual QtTest data rows; parser checks are grouped into named test slots.
+Checks also run in release builds.
+
+To build tests separately against an existing core build:
 
 ```sh
-mkdir -p /tmp/dbc_decoder_test_build
-cd /tmp/dbc_decoder_test_build
-qmake /absolute/path/to/dbc/tests/dbc_decoder_test.pro
+mkdir /tmp/dbc-tests-build
+cd /tmp/dbc-tests-build
+qmake6 /absolute/path/to/dbc/tests/tests.pro \
+  DBC_CORE_BUILD_DIR=/absolute/path/to/build/core
 make
-./dbc_decoder_test
+make check
 ```
 
-The executable returns a nonzero exit code if any case fails. Checks remain
-active in release builds and do not depend on `assert` or an external test framework.
+`parser_tests.pri` and `decoder_tests.pri` include the test sources.
+`../core/core.pri` supplies the library include path and linkage.
+
+## Decoder coverage
 
 Coverage includes Motorola bit numbering within and across bytes, unaligned
 signals, signed values, scaling, 64-bit extraction, signed/unsigned boundary values
@@ -27,18 +42,7 @@ signals, signed values, scaling, 64-bit extraction, signed/unsigned boundary val
 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 dbc_statement_handler.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 coverage
 
 Parser tests cover standard and extended CAN IDs, whitespace, payload storage
 boundaries, missing fields, malformed and overflowing numbers, reserved ID bits,