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