assertIsDisplayed

Asserts the matched node is displayed, with off-screen semantics.

The test harness never attaches its root to a window, so no native peer is realized (with or without a display), java.awt.Component.isShowing is permanently false, and it cannot be used. Instead, "displayed" here means the node has non-zero bounds produced by the forced layout pass the harness runs - a real width and height assigned by its ancestor's layout manager within the query's root, the harness root or the window's own content for a window-scoped query.

What this catches off-screen, without requiring an on-screen peer, is a node a layout collapsed to zero size. A node that is no longer in the tree is reported by the query failing to resolve; assert its absence with assertDoesNotExist, and whether a node has been hidden with assertIsVisible.