Closes #16

tests/README.md

@@ -24,7 +24,7 @@ make -j
 make check
 ```
 
-Or run `./tests/dbc_tests` directly. Parser, decoder, lifetime, and additional coverage
+Or run `./tests/dbc_tests` directly. Parser, decoder, 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.
@@ -41,7 +41,8 @@ make check
 ```
 
 `parser_tests.pri` and `decoder_tests.pri` include the original test sources;
-`tests.pro` also includes `dbc_coverage_test.cpp` and `dbc_lifetime_test.cpp`.
+`tests.pro` also includes `dbc_coverage_test.cpp`, `dbc_lifetime_test.cpp`, and
+`dbc_validation_test.cpp`.
 `../core/core.pri` supplies the library include path and linkage.
 
 ## Decoder coverage
@@ -52,10 +53,11 @@ signals, signed values, scaling, 64-bit extraction, signed/unsigned boundary val
 payloads, and Intel regression cases. Frame validity means the definition was
 found; frame status reports unknown frames, short payloads, and signal errors.
 Tests exercise empty/short/exact/long payloads, ignored trailing bytes, signals
-outside declared DLC, invalid enum metadata and overflowing start bits, and
-preservation of successful signals. Physical conversion checks cover NaN/Inf
-parameters, multiplication/addition overflow, finite limits, signed/unsigned raw
-retention, and raw selector activation after physical conversion failure.
+outside declared DLC, invalid enum metadata and overflowing start bits rejected
+at construction, and preservation of successful signals on partial payloads.
+Physical conversion checks cover NaN/Inf parameters rejected at construction,
+multiplication/addition overflow, finite limits, signed/unsigned raw retention,
+and raw selector activation after physical conversion failure.
 
 ## Parser coverage
 
@@ -116,8 +118,9 @@ of invalid markers, selector references/ranges, overlaps, and SG_MUL_VAL_.
 
 `dbc_coverage_test.cpp` runs as part of `dbc_tests`. It covers signed boundaries
 below 64 bits, deterministic extraction comparisons for both byte orders across
-lengths 1–64, frame lookup failures, exact decode statuses, malformed runtime
-multiplexing, PGN boundaries, comment handling, file formatting, metadata copying
+lengths 1–64, frame lookup failures, exact decode statuses, construction rejection
+of malformed runtime multiplexing, PGN boundaries, comment handling, file
+formatting, metadata copying
 and source lifetime, physical conversion, and TypeFactory registration/creation.
 Direct resolver tests construct ambiguous databases through the public metadata
 API, verify source locations, and check that ambiguous targets receive no values.
@@ -141,3 +144,19 @@ duplicate runtime keys, including manually supplied parsed metadata. Failed relo
 leaves the active database intact; empty reload clears it. Invalid/unknown results
 and insufficient payloads retain their documented ownership and status behavior.
 Inactive branches and unavailable selectors also retain definitions across reload.
+
+## Database validation coverage
+
+`dbc_validation_test.cpp` checks direct construction and manually assembled
+`DbcDatabase` input to `DbcDecodeBuilder`: standard/extended CAN ID limits,
+encoded/reserved ID bits, duplicate keys, lengths 0/1–64/65/UINT32_MAX,
+Intel/Motorola payload boundaries and overflowing start bits, invalid enums,
+NaN and both infinities in every numeric parameter, and reversed physical ranges.
+Selector tests include missing, duplicate, and signed selectors, branch ranges,
+UINT64_MAX selection, mixed-order overlaps, and exclusive branches sharing bits.
+Valid definitions cover the full byte-count storage range, including zero-byte
+frames without signals and 255-byte frames. Existing extraction tests cover
+lengths 1–64. Snapshot tests mutate retained frame, signal, and description aliases
+after rvalue construction, and verify unchanged lookups and metadata. Failed
+constructor/builder replacement preserves the active snapshot; clear removes its
+index while saved handles remain alive.