skillguard/artifacts/api-server/src/lib/skillFingerprint.test.ts

import { describe, it, expect } from "vitest";
import {
  hashText,
  hashBytes,
  computeFingerprint,
  jaccard,
} from "./skillFingerprint";

describe("hashText / hashBytes", () => {
  it("produces a stable sha256 hex digest", () => {
    const h = hashText("hello world");
    expect(h).toBe(
      "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9",
    );
    expect(h).toMatch(/^[0-9a-f]{64}$/);
  });

  it("agrees between hashText and hashBytes for the same content", () => {
    const text = "some skill content\nwith two lines";
    expect(hashText(text)).toBe(hashBytes(Buffer.from(text, "utf-8")));
  });

  it("changes when the content changes", () => {
    expect(hashText("a")).not.toBe(hashText("b"));
  });
});

describe("computeFingerprint", () => {
  const files = [
    { path: "SKILL.md", hash: "aaa" },
    { path: "scripts/run.sh", hash: "bbb" },
    { path: "data.json", hash: "ccc" },
  ];

  it("is stable across calls with the same input", () => {
    expect(computeFingerprint(files)).toBe(computeFingerprint(files));
  });

  it("is independent of the order files are supplied in", () => {
    const reordered = [files[2], files[0], files[1]];
    expect(computeFingerprint(reordered)).toBe(computeFingerprint(files));
  });

  it("changes when a file's content hash changes", () => {
    const changed = [
      files[0],
      { path: "scripts/run.sh", hash: "DIFFERENT" },
      files[2],
    ];
    expect(computeFingerprint(changed)).not.toBe(computeFingerprint(files));
  });

  it("changes when a file's path changes", () => {
    const renamed = [
      { path: "SKILL.md", hash: "aaa" },
      { path: "scripts/start.sh", hash: "bbb" },
      files[2],
    ];
    expect(computeFingerprint(renamed)).not.toBe(computeFingerprint(files));
  });

  it("changes when a file is added or removed", () => {
    const fewer = [files[0], files[1]];
    expect(computeFingerprint(fewer)).not.toBe(computeFingerprint(files));
  });

  it("returns a 64-char hex digest", () => {
    expect(computeFingerprint(files)).toMatch(/^[0-9a-f]{64}$/);
  });
});

describe("jaccard", () => {
  it("is 1 for identical non-empty sets", () => {
    expect(jaccard(new Set(["a", "b"]), new Set(["a", "b"]))).toBe(1);
  });

  it("is 0 for disjoint sets", () => {
    expect(jaccard(new Set(["a"]), new Set(["b"]))).toBe(0);
  });

  it("computes intersection over union for partial overlap", () => {
    // intersection {a} = 1, union {a,b,c} = 3
    expect(jaccard(new Set(["a", "b"]), new Set(["a", "c"]))).toBeCloseTo(
      1 / 3,
      10,
    );
  });

  it("is symmetric", () => {
    const a = new Set(["a", "b", "c"]);
    const b = new Set(["b", "c", "d"]);
    expect(jaccard(a, b)).toBe(jaccard(b, a));
  });

  it("treats two empty sets as 0 (no overlap to report)", () => {
    expect(jaccard(new Set(), new Set())).toBe(0);
  });
});