Closes #17

tests/README.md

@@ -24,7 +24,7 @@ make -j
 make check
 ```
 
-Or run `./tests/dbc_tests` directly. Parser, decoder, lifetime, validation, and additional coverage
+Or run `./tests/dbc_tests` directly. Parser, decoder, pipeline, lifetime, validation, and additional coverage
 suites run, and the executable returns nonzero when any suite fails. Decoder cases appear as
 individual QtTest data rows; parser checks are grouped into named test slots.
 Checks also run in release builds.
@@ -41,8 +41,8 @@ make check
 ```
 
 `parser_tests.pri` and `decoder_tests.pri` include the original test sources;
-`tests.pro` also includes `dbc_coverage_test.cpp`, `dbc_lifetime_test.cpp`, and
-`dbc_validation_test.cpp`.
+`tests.pro` also includes `dbc_coverage_test.cpp`, `dbc_lifetime_test.cpp`,
+`dbc_validation_test.cpp`, and `dbc_pipeline_test.cpp`.
 `../core/core.pri` supplies the library include path and linkage.
 
 ## Decoder coverage
@@ -167,3 +167,17 @@ all lengths 1–64, for both byte orders. Zero/65-bit lengths and uint32 maximum
 inputs are rejected. Builder snapshots survive input mutation and destruction;
 failed replacement with duplicate frame or signal keys preserves the existing
 frame and signal lookups.
+
+## End-to-end pipeline coverage
+
+`dbc_pipeline_test.cpp` parses temporary DBC files and checks independent expected
+metadata against the parser, runtime builder, and tree builder. It exercises
+standard and extended frames with the same numeric ID and signal name, Intel
+and signed Motorola decoding, scaling, raw value descriptions, basic multiplexing,
+PGN metadata, receivers, units, ranges, and frame/signal comments. Tree checks
+include node types, payloads, parents, rows, names, and child counts.
+
+Empty and headers-only fixtures produce an empty runtime database and a valid
+empty tree root. Replacement fixtures change definitions, metadata and decoded
+values, remove old lookup keys, and then clear both outputs through an empty
+fixture. Saved decoded results and trees retain their original metadata.