worker: improve code coverage
It adds tests for the worker getHeadSnapshot function and assignEnvironmentData Refs: lib/internal/worker.js.html#L412 and lib/internal/worker.js.html#L114
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
It adds tests for the worker getHeadSnapshot function and assignEnvironmentData Refs: lib/internal/worker.js.html#L412 and lib/internal/worker.js.html#L114