team-split.util.spec.ts

import { BadRequestException } from '@nestjs/common';
import {
  computeSplitShares,
  validateSplitPercentages,
} from './team-split.util';

describe('team split percentage math', () => {
  it('accepts splits that sum to exactly 100', () => {
    expect(() =>
      validateSplitPercentages([
        { percentage: 40 },
        { percentage: 40 },
        { percentage: 20 },
      ]),
    ).not.toThrow();
  });

  it('accepts splits within floating point tolerance of 100', () => {
    expect(() =>
      validateSplitPercentages([
        { percentage: 33.33 },
        { percentage: 33.33 },
        { percentage: 33.34 },
      ]),
    ).not.toThrow();
  });

  it('rejects splits that sum to less than 100', () => {
    expect(() =>
      validateSplitPercentages([{ percentage: 40 }, { percentage: 40 }]),
    ).toThrow(BadRequestException);
  });

  it('rejects splits that sum to more than 100', () => {
    expect(() =>
      validateSplitPercentages([{ percentage: 60 }, { percentage: 60 }]),
    ).toThrow(BadRequestException);
  });

  it('rejects a zero or negative percentage', () => {
    expect(() =>
      validateSplitPercentages([{ percentage: 0 }, { percentage: 100 }]),
    ).toThrow(BadRequestException);
  });

  it('rejects an empty split list', () => {
    expect(() => validateSplitPercentages([])).toThrow(BadRequestException);
  });

  it('computeSplitShares divides an amount proportionally', () => {
    const shares = computeSplitShares(1000, [
      { percentage: 40 },
      { percentage: 40 },
      { percentage: 20 },
    ]);
    expect(shares).toEqual([400, 400, 200]);
  });

  it('computeSplitShares handles uneven thirds without losing precision beyond 7dp', () => {
    const shares = computeSplitShares(100, [
      { percentage: 33.33 },
      { percentage: 33.33 },
      { percentage: 33.34 },
    ]);
    const total = shares.reduce((a, b) => a + b, 0);
    expect(total).toBeCloseTo(100, 5);
  });
});