Coverage

How much of each engine its tests reach. Generated on every docs build, so this page describes the commit it was built from rather than a number somebody typed once.

Engine	Lines	Branches	Functions	Tests	Measured with
SwiftUI	93.42%	89.77% (regions)	85.83%	112	llvm-cov
Compose	92.20%	80.94%	89.95%	114	Kover
TypeScript	98.10%	94.53%	98.60%	172	node –experimental-test-coverage
React binding	98.10%	85.48%	93.33%	19	node –experimental-test-coverage
CLI	98.85%	93.59%	97.97%	101	node –experimental-test-coverage

Read these as a floor, not a score. Every engine passes the same 1620 conformance vectors, which is the definition of correct here; coverage only says how much of each implementation those vectors plus its own tests happen to execute. A line nobody runs is a line nobody has checked, which is why the numbers are worth publishing, but a high number is not evidence of conformance and a lower one is not evidence of a defect.

Swift is measured with llvm-cov, which counts regions rather than branches; the column is labelled accordingly. Kotlin is measured with Kover, and the three TypeScript packages with Node’s built-in coverage, which also enforces a floor on every test run so a regression fails CI rather than showing up here.

The uncovered remainder is mostly defensive: branches that exist because a type system cannot prove they are unreachable, and error paths for inputs the gate has already rejected.