spec.js

/*jshint node:true, mocha:true */

'use strict';

require('should');

var decimalFactory = require('arbitrary-precision');
var adapter = require('../src/floating-adapter');

var Decimal = decimalFactory(adapter);
var Floating = adapter.getInstance();

describe('linear operations with floating', function() {
  describe('constructor', function() {
    it('should throw if called without new', function() {
      (function() {
        /*jshint -W064*/
        Decimal('1');
      }).should.throw();
    });

    it('should throw if used without a string', function() {
      (function() {
        new Decimal(1);
      }).should.throw(TypeError);
    });
  });

  describe('precision', function() {
    var initialPrecision = Decimal.getPrecision();

    it('should be able to get the current precision', function() {
      Decimal.getPrecision().should.have.type('number');

      new Decimal('1').div(new Decimal('3')).toString().should.be.exactly('0.3333333333333333');
    });

    it('should be able to set the current precision', function() {
      Decimal.setPrecision(42);
      Decimal.getPrecision().should.be.exactly(42);
      new Decimal('1').div(new Decimal('3')).toString().should.be.exactly('0.3333333333333333');

      Decimal.setPrecision(initialPrecision);
    });
  });

  describe('operations', function() {
    it('should have a plus method', function() {
      new Decimal('0.1').plus(new Decimal('0.2')).valueOf().should.be.exactly(0.1 + 0.2);
    });

    it('should have a minus method', function() {
      new Decimal('0.3').minus(new Decimal('0.1')).valueOf().should.be.exactly(0.3 - 0.1);
    });

    it('should have a times method', function() {
      new Decimal('0.6').times(new Decimal('3')).valueOf().should.be.exactly(0.6 * 3);
    });

    it('should have a div method', function() {
      new Decimal('0.3').div(new Decimal('0.2')).valueOf().should.be.exactly(0.3 / 0.2);
    });

    it('should have a mod method', function() {
      adapter.mod(new Floating(12), new Floating(5)).valueOf().should.be.exactly(2);
    });

    it('should have an sqrt method', function() {
      adapter.sqrt(new Floating(16)).valueOf().should.be.exactly(4);
    });

    it('should have a pow method', function() {
      new Decimal('2').pow(new Decimal('3')).valueOf().should.be.exactly(8);
      new Decimal('81').pow(new Decimal('0.5')).valueOf().should.be.exactly(9);
    });

    it('should have an equals method', function() {
      adapter.equals(new Decimal('2').val(), new Decimal('2').val()).should.be.exactly(true);
      adapter.equals(new Decimal('2').val(), new Decimal('3').val()).should.be.exactly(false);
    });

    it('should have a gt method', function() {
      adapter.gt(new Floating(2), new Floating(2)).should.be.exactly(false);
      adapter.gt(new Floating(2), new Floating(3)).should.be.exactly(false);
      adapter.gt(new Floating(2), new Floating(1)).should.be.exactly(true);
    });

    it('should have a gte method', function() {
      adapter.gte(new Floating(2), new Floating(2)).should.be.exactly(true);
      adapter.gte(new Floating(2), new Floating(3)).should.be.exactly(false);
      adapter.gte(new Floating(2), new Floating(1)).should.be.exactly(true);
    });

    it('should have a lt method', function() {
      adapter.lt(new Floating(2), new Floating(2)).should.be.exactly(false);
      adapter.lt(new Floating(2), new Floating(3)).should.be.exactly(true);
      adapter.lt(new Floating(2), new Floating(1)).should.be.exactly(false);
    });

    it('should have a lte method', function() {
      adapter.lte(new Floating(2), new Floating(2)).should.be.exactly(true);
      adapter.lte(new Floating(2), new Floating(3)).should.be.exactly(true);
      adapter.lte(new Floating(2), new Floating(1)).should.be.exactly(false);
    });

    it('should have a cmp method', function() {
      adapter.cmp(new Floating(2), new Floating(2)).valueOf().should.be.exactly(0);
      adapter.cmp(new Floating(2), new Floating(3)).valueOf().should.be.exactly(-1);
      adapter.cmp(new Floating(2), new Floating(1)).valueOf().should.be.exactly(1);
    });

    it('should have a abs method', function() {
      adapter.abs(new Floating(16)).valueOf().should.be.exactly(16);
      adapter.abs(new Floating(-5)).valueOf().should.be.exactly(5);
    });
  });

  describe('toString, valueOf and JSON', function() {
    it('should be able to return a string representation', function() {
      var decimalThird = new Decimal('1').div(new Decimal('3'));

      decimalThird.toString().should.be.exactly('0.3333333333333333')
        .and.exactly(decimalThird.toJSON());

      decimalThird.valueOf().should.be.exactly(1/3);
    });

    it('should play nicely with Number()', function() {
      var decimalThird = new Decimal('1').div(new Decimal('3'));

      Number(decimalThird).should.be.exactly(1/3);
    });

    it('should play nicely with JSON.stringify()', function() {
      var Decimal40 = decimalFactory(adapter);

      Decimal40.setPrecision(40);

      var decimalThird = new Decimal40('1').div(new Decimal40('3'));
      var stringified = JSON.stringify(decimalThird);

      stringified.should.be.exactly('"0.3333333333333333"');

      JSON.parse(stringified, Decimal40.reviver).should.eql(decimalThird);
    });
  });
});