Initial Commit

packages/foundation/random/pseudo-random/src/utils/sample.extra.test.ts

@@ -0,0 +1,26 @@
+import { describe, expect, it } from "@suaveplan/testing/runner";
+import type { Rng } from "@suaveplan/types";
+import { weightedChoice } from "./sample.js";
+
+class FakeFloatRng implements Rng {
+    public constructor(protected value: number) {}
+    public nextUint32(): number {
+        return 0;
+    }
+    public nextFloat(): number {
+        return this.value;
+    }
+}
+
+describe("weightedChoice floating-point fallback", () => {
+    it("returns last index when target >= total (FP edge)", {
+        timeout: 5000,
+    }, () => {
+        // A nextFloat value of exactly 1 would make target === total,
+        // so `target < acc` never fires and the function must fall through
+        // to the defensive final return.
+        const rng = new FakeFloatRng(1);
+        const idx = weightedChoice([1, 2, 3], rng);
+        expect(idx).toBe(2);
+    });
+});