import { describe, it, expect } from "vitest";
import { factorize } from "../src/index.js";
describe("factorize", () => {
describe("正常系", () => {
it("12を素因数分解すると[2, 2, 3]", () => {
expect(factorize(12).factors).toEqual([2, 2, 3]);
});
it("素数は自身のみ", () => {
expect(factorize(7).factors).toEqual([7]);
expect(factorize(13).factors).toEqual([13]);
expect(factorize(97).factors).toEqual([97]);
});
it("1は[1]を返す", () => {
expect(factorize(1).factors).toEqual([1]);
});
it("2は[2]を返す", () => {
expect(factorize(2).factors).toEqual([2]);
});
it("大きな合成数を正しく分解する", () => {
expect(factorize(100).factors).toEqual([2, 2, 5, 5]);
expect(factorize(360).factors).toEqual([2, 2, 2, 3, 3, 5]);
expect(factorize(1000).factors).toEqual([2, 2, 2, 5, 5, 5]);
});
it("2の累乗を正しく分解する", () => {
expect(factorize(8).factors).toEqual([2, 2, 2]);
expect(factorize(64).factors).toEqual([2, 2, 2, 2, 2, 2]);
expect(factorize(1024).factors).toEqual([2, 2, 2, 2, 2, 2, 2, 2, 2, 2]);
});
it("大きな素数を処理できる", () => {
expect(factorize(104729).factors).toEqual([104729]);
});
it("15桁の数値を処理できる", () => {
const result = factorize(999999999999999);
const product = result.factors.reduce((a, b) => a * b, 1);
expect(product).toBe(999999999999999);
});
});
describe("境界値", () => {
it("最小値1を処理できる", () => {
expect(factorize(1).factors).toEqual([1]);
});
it("最小の素数2を処理できる", () => {
expect(factorize(2).factors).toEqual([2]);
});
it("最小の合成数4を処理できる", () => {
expect(factorize(4).factors).toEqual([2, 2]);
});
});
describe("結果の検証", () => {
it("素因数の積が元の数と等しい", () => {
const testCases = [12, 100, 360, 1000, 12345, 99999];
for (const n of testCases) {
const { factors } = factorize(n);
const product = factors.reduce((a, b) => a * b, 1);
expect(product).toBe(n);
}
});
it("結果は昇順にソートされている", () => {
const testCases = [12, 100, 360, 1000, 12345, 99999];
for (const n of testCases) {
const { factors } = factorize(n);
const sorted = [...factors].sort((a, b) => a - b);
expect(factors).toEqual(sorted);
}
});
});
describe("割り算回数", () => {
it("1の場合は割り算回数0", () => {
expect(factorize(1).divisionCount).toBe(0);
});
it("割り算回数が返される", () => {
const result = factorize(12);
expect(result.divisionCount).toBeGreaterThan(0);
});
});
});
