onChild
Source set: Common
@CheckResult
fun SemanticsNodeInteraction.onChild(): SemanticsNodeInteractionReturns exactly one child of this node.
Use this only if this node has exactly one child.
Any subsequent operation on its result will expect exactly one element found (unless SemanticsNodeInteraction.assertDoesNotExist is used) and will throw AssertionError if none or more than one element is found.
