tests/dmqim.test.ts

import { describe, it, expect } from 'vitest';
import { dmqimEmbed, dmqimExtractSoft, dmqimExtractHard } from '../core/dmqim.js';

describe('DM-QIM', () => {
  it('should embed and extract bit 0 correctly', () => {
    const coeff = 42.5;
    const delta = 10;
    const dither = 3.7;

    const embedded = dmqimEmbed(coeff, 0, delta, dither);
    const hard = dmqimExtractHard(embedded, delta, dither);
    expect(hard).toBe(0);
  });

  it('should embed and extract bit 1 correctly', () => {
    const coeff = 42.5;
    const delta = 10;
    const dither = 3.7;

    const embedded = dmqimEmbed(coeff, 1, delta, dither);
    const hard = dmqimExtractHard(embedded, delta, dither);
    expect(hard).toBe(1);
  });

  it('should produce correct soft decisions', () => {
    const delta = 20;
    const dither = 5.0;

    for (let bit = 0; bit <= 1; bit++) {
      const embedded = dmqimEmbed(50, bit, delta, dither);
      const soft = dmqimExtractSoft(embedded, delta, dither);

      if (bit === 1) {
        expect(soft).toBeGreaterThan(0);
      } else {
        expect(soft).toBeLessThanOrEqual(0);
      }
    }
  });

  it('should work with various coefficient values and dithers', () => {
    const delta = 15;
    for (let trial = 0; trial < 100; trial++) {
      const coeff = (Math.random() - 0.5) * 200;
      const dither = (Math.random() - 0.5) * delta;
      const bit = Math.random() > 0.5 ? 1 : 0;

      const embedded = dmqimEmbed(coeff, bit, delta, dither);
      const extracted = dmqimExtractHard(embedded, delta, dither);
      expect(extracted).toBe(bit);
    }
  });
});