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import { consistentHashingChoice } from "./sticky";
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describe("tests of consistentHashingChoice", () => {
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  it("throws when set has size 0", () => {
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    expect(() => consistentHashingChoice(new Set(), "x")).toThrow("size");
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  });
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  it("for size one it just returns the unique item", () => {
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    expect(consistentHashingChoice(new Set(["foo"]), "bar")).toEqual("foo");
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  });
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  it("for size 3 it gives the same result every time for the same input (and also that it's not stupidly slow)", () => {
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    const v = new Set(["a", "b", "x"]);
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    const resource = "thing";
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    const choice = consistentHashingChoice(v, resource);
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    expect(v.has(choice)).toBe(true);
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    for (let i = 0; i < 1000; i++) {
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      expect(consistentHashingChoice(v, resource)).toBe(choice);
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    }
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  });
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  it("the results are uniformly distributed when the resources are different", () => {
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    const v = new Set(["a", "b", "x"]);
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    const c = { a: 0, b: 0, x: 0 };
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    for (let i = 0; i < 1000; i++) {
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      c[consistentHashingChoice(v, `${i}`)] += 1;
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    }
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    // just roughly in the direction of uniform...
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    expect(c.a).toBeGreaterThan(250);
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    expect(c.b).toBeGreaterThan(250);
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    expect(c.x).toBeGreaterThan(250);
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  });
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});
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