test(browser): drive a canvas-under-shadow-root fixture end to end

test/browser/testdata/shadow/spec.ts

@@ -0,0 +1,17 @@
+import { always, extract, taps } from "@sanderling/spec";
+
+const bumps = extract((s) => {
+  const el = s.ax.find({ id: "count" });
+  return el ? parseInt(el.text, 10) || 0 : 0;
+}).named("bumps");
+
+// The button, the counter that records the taps, and the canvas that services
+// them all live inside a shadow root. A host that stops at the shadow boundary
+// enumerates no target to tap and resolves no selector to read, so the counter
+// can never leave zero: this property firing IS the evidence that both the
+// enumeration and the selector lookup crossed the boundary.
+const counterNeverMoves = always(() => bumps.current === 0);
+
+export const properties = { counterNeverMoves };
+
+export const actionsRoot = taps;