diff --git a/internal/integration/testdata/counter/spec.ts b/internal/integration/testdata/counter/spec.ts
new file mode 100644
index 0000000..64cdeb4
--- /dev/null
+++ b/internal/integration/testdata/counter/spec.ts
@@ -0,0 +1,18 @@
+import { always, extract, taps } from "@sanderling/spec";
+
+const counter = extract((s) => {
+  const el = s.ax.find({ id: "counter" });
+  return el ? parseInt(el.text, 10) || 0 : 0;
+}).named("counter");
+
+// The + and - buttons each move the counter by exactly 1, so no step ever
+// changes it by more than 1. A bug that double-applied a click would break this.
+const changesByAtMostOne = always(() => {
+  const previous = counter.previous;
+  if (previous === undefined) return true;
+  return Math.abs(counter.current - previous) <= 1;
+});
+
+export const properties = { changesByAtMostOne };
+
+export const actionsRoot = taps;
diff --git a/internal/integration/testdata/throwing/spec.ts b/internal/integration/testdata/throwing/spec.ts
new file mode 100644
index 0000000..4803b81
--- /dev/null
+++ b/internal/integration/testdata/throwing/spec.ts
@@ -0,0 +1,6 @@
+import { taps } from "@sanderling/spec";
+import { noUncaughtExceptions } from "@sanderling/spec/defaults/properties";
+
+export const properties = { noUncaughtExceptions };
+
+export const actionsRoot = taps;