Command	Scope
`yarn test:unit`	Playback and DASH regressions, public contracts against released/current code, and JS/TS fixture loading
`yarn test:node`	Unit contracts plus toolchain and documentation build failure propagation
`yarn test`	Node checks and the committed baseline/tooling tests in refactor/scripts
`yarn ci:check`	Toolchain, plan, read-only lint, types, then yarn test
`yarn test:imports`	Existing distribution import smoke examples; run after building

helpers/load.js owns source and artifact selection. loadModules bundles named internal modules with esbuild and requires exactly one JS/TS source file. loadPackage uses the repository Vite configuration without writing distribution files; it requires a single self-contained JavaScript chunk. These loaders transpile but do not replace yarn typecheck.

helpers/playback.js creates the controlled media facade used by the original playback regressions. It models only the exercised methods and events. It is not HTMLMediaElement validation; actual playback remains in browser tests.

contracts/emitter.js owns public assertions, independent of module layout. public-behavior.test.js runs them against the integrity-checked published core and current bundled source. The combined chain/context contract corresponds to BASE-03 EVENT.chain and EVENT.context-arguments; other EVENT IDs retain their baseline names. Exceptions, callback identity, mutation during dispatch and once reentry must not be weakened during migration.

Set ARTPLAYER_TEST_CORE to a built .js, .legacy.js or .mjs core file to add a candidate to the same public-contract run, then execute node --test test/public-behavior.test.js. An invalid path/export fails the run. This is a narrow event contract check, not isolated package installation or complete API compatibility; ENG-07 owns tarball consumption.

When a production module moves, update its loader mapping and its maintenance documentation, preserving the behavioral assertions. New contracts belong in contracts/; test-specific controlled state belongs in helpers/. Do not modify frozen refactor/fixtures or baseline captures just to pass changed behavior. Record historical defects and candidate fixes separately.

Real browser tests

test/utils.test.js compares the published and current utilities, including exact formatting, subtitle text, property/merge behavior, controlled timers and the full utility export surface. It accepts the same ARTPLAYER_TEST_CORE option for all three artifact formats. The merge prototype fix is a candidate assertion alongside a published-only defect observation. test/types/utils-source.ts checks strict internal source inference without changing the still-separate public declaration contract. Browser utility tests exercise actual downloads, Blob URL contents and cleanup when a controlled click fails.

See browser/README.md for yarn test:browser, browser installation, published/current combinations, media fixtures, candidate mapping and failure reports. These tests are separate from the fast Node suite and run in the Browser playback smoke CI job.