openzeppelin-contracts/test/utils/math/Math.test.js

const { BN, constants, expectRevert } = require('@openzeppelin/test-helpers');
const { expect } = require('chai');
const { MAX_UINT256 } = constants;
const { Rounding } = require('../../helpers/enums.js');

const MathMock = artifacts.require('MathMock');

contract('Math', function (accounts) {
  const min = new BN('1234');
  const max = new BN('5678');
  const MAX_UINT256_SUB1 = MAX_UINT256.sub(new BN('1'));
  const MAX_UINT256_SUB2 = MAX_UINT256.sub(new BN('2'));

  beforeEach(async function () {
    this.math = await MathMock.new();
  });

  describe('max', function () {
    it('is correctly detected in first argument position', async function () {
      expect(await this.math.max(max, min)).to.be.bignumber.equal(max);
    });

    it('is correctly detected in second argument position', async function () {
      expect(await this.math.max(min, max)).to.be.bignumber.equal(max);
    });
  });

  describe('min', function () {
    it('is correctly detected in first argument position', async function () {
      expect(await this.math.min(min, max)).to.be.bignumber.equal(min);
    });

    it('is correctly detected in second argument position', async function () {
      expect(await this.math.min(max, min)).to.be.bignumber.equal(min);
    });
  });

  describe('average', function () {
    function bnAverage (a, b) {
      return a.add(b).divn(2);
    }

    it('is correctly calculated with two odd numbers', async function () {
      const a = new BN('57417');
      const b = new BN('95431');
      expect(await this.math.average(a, b)).to.be.bignumber.equal(bnAverage(a, b));
    });

    it('is correctly calculated with two even numbers', async function () {
      const a = new BN('42304');
      const b = new BN('84346');
      expect(await this.math.average(a, b)).to.be.bignumber.equal(bnAverage(a, b));
    });

    it('is correctly calculated with one even and one odd number', async function () {
      const a = new BN('57417');
      const b = new BN('84346');
      expect(await this.math.average(a, b)).to.be.bignumber.equal(bnAverage(a, b));
    });

    it('is correctly calculated with two max uint256 numbers', async function () {
      const a = MAX_UINT256;
      expect(await this.math.average(a, a)).to.be.bignumber.equal(bnAverage(a, a));
    });
  });

  describe('ceilDiv', function () {
    it('does not round up on exact division', async function () {
      const a = new BN('10');
      const b = new BN('5');
      expect(await this.math.ceilDiv(a, b)).to.be.bignumber.equal('2');
    });

    it('rounds up on division with remainders', async function () {
      const a = new BN('42');
      const b = new BN('13');
      expect(await this.math.ceilDiv(a, b)).to.be.bignumber.equal('4');
    });

    it('does not overflow', async function () {
      const b = new BN('2');
      const result = new BN('1').shln(255);
      expect(await this.math.ceilDiv(MAX_UINT256, b)).to.be.bignumber.equal(result);
    });

    it('correctly computes max uint256 divided by 1', async function () {
      const b = new BN('1');
      expect(await this.math.ceilDiv(MAX_UINT256, b)).to.be.bignumber.equal(MAX_UINT256);
    });
  });

  describe('muldiv', function () {
    it('divide by 0', async function () {
      await expectRevert.unspecified(this.math.mulDiv(1, 1, 0, Rounding.Down));
    });

    describe('does round down', async function () {
      it('small values', async function () {
        expect(await this.math.mulDiv('3', '4', '5', Rounding.Down)).to.be.bignumber.equal('2');
        expect(await this.math.mulDiv('3', '5', '5', Rounding.Down)).to.be.bignumber.equal('3');
      });

      it('large values', async function () {
        expect(await this.math.mulDiv(
          new BN('42'),
          MAX_UINT256_SUB1,
          MAX_UINT256,
          Rounding.Down,
        )).to.be.bignumber.equal(new BN('41'));

        expect(await this.math.mulDiv(
          new BN('17'),
          MAX_UINT256,
          MAX_UINT256,
          Rounding.Down,
        )).to.be.bignumber.equal(new BN('17'));

        expect(await this.math.mulDiv(
          MAX_UINT256_SUB1,
          MAX_UINT256_SUB1,
          MAX_UINT256,
          Rounding.Down,
        )).to.be.bignumber.equal(MAX_UINT256_SUB2);

        expect(await this.math.mulDiv(
          MAX_UINT256,
          MAX_UINT256_SUB1,
          MAX_UINT256,
          Rounding.Down,
        )).to.be.bignumber.equal(MAX_UINT256_SUB1);

        expect(await this.math.mulDiv(
          MAX_UINT256,
          MAX_UINT256,
          MAX_UINT256,
          Rounding.Down,
        )).to.be.bignumber.equal(MAX_UINT256);
      });
    });

    describe('does round up', async function () {
      it('small values', async function () {
        expect(await this.math.mulDiv('3', '4', '5', Rounding.Up)).to.be.bignumber.equal('3');
        expect(await this.math.mulDiv('3', '5', '5', Rounding.Up)).to.be.bignumber.equal('3');
      });

      it('large values', async function () {
        expect(await this.math.mulDiv(
          new BN('42'),
          MAX_UINT256_SUB1,
          MAX_UINT256,
          Rounding.Up,
        )).to.be.bignumber.equal(new BN('42'));

        expect(await this.math.mulDiv(
          new BN('17'),
          MAX_UINT256,
          MAX_UINT256,
          Rounding.Up,
        )).to.be.bignumber.equal(new BN('17'));

        expect(await this.math.mulDiv(
          MAX_UINT256_SUB1,
          MAX_UINT256_SUB1,
          MAX_UINT256,
          Rounding.Up,
        )).to.be.bignumber.equal(MAX_UINT256_SUB1);

        expect(await this.math.mulDiv(
          MAX_UINT256,
          MAX_UINT256_SUB1,
          MAX_UINT256,
          Rounding.Up,
        )).to.be.bignumber.equal(MAX_UINT256_SUB1);

        expect(await this.math.mulDiv(
          MAX_UINT256,
          MAX_UINT256,
          MAX_UINT256,
          Rounding.Up,
        )).to.be.bignumber.equal(MAX_UINT256);
      });
    });
  });
});