Every .riv and .expect in this folder is produced by packages/rive_core/test/matrix/emit_matrix_test.dart from the specs in slices.dart.
That test verifies these files by default and fails if they do not match the specs. To regenerate after changing a spec:
cd packages/rive_core RIVE_MATRIX_WRITE=1 flutter test test/matrix/emit_matrix_test.dart
Verifying is the default on purpose. A plain flutter test runs every file under test/, so an emitter that always wrote would regenerate the corpus on the Dart CI job while the C++ job kept testing whatever is committed. Edit a slice, forget to regenerate, and the two halves silently test different things with nothing red anywhere. Verifying turns that into a failure on the PR that caused it.
Do not add hand-authored files here: the C++ runner (runtime/layout_matrix_test.cpp) assumes every .riv has an .expect sibling, and the verifier reports anything it did not generate as unexpected.
Expected values are DERIVED from the declared geometry in slices.dart, never recorded from a run. If a fixture starts failing, the question is whether the spec or the implementation is wrong — not which one to re-record.
The same specs and the same derivations are checked twice:
runtime/layout_matrix_test.cpp reads the .riv + .expect pairs here. This is the runtime that ships.packages/rive_core/test/matrix/dart_conformance_test.dart builds the same scenes live and checks the editor's own layout pipeline. It skips what rive_core cannot mount on its own (nested artboards, data-bound lists, riv version gates) and counts those out loud rather than passing silently.A cell that only fails on one side is a runtime divergence, which is the whole reason for running both.
.expect| tag | meaning |
|---|---|
C | the correct value; asserted directly |
L | a value the runtime must NOT produce; the runner asserts the actual value DIFFERS. Only written for a field with no C, since a C already fails on every wrong value including this one |
X | a known, reproduced defect. The value recorded is still the CORRECT one and the assertion is inverted: a mismatch warns, a MATCH fails and tells whoever fixed it to clear the knownDefect marker in the spec |