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chai-bignumber

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Chai assertions for comparing arbitrary-precision decimals using the bignumber.js library.

Installation

npm install --save-dev chai-bignumber

Usage

var chai = require('chai');

//use default BigNumber
chai.use(require('chai-bignumber')());

//use custom BigNumber
chai.use(require('chai-bignumber')(BigNumber));

Assertions

The following assertion methods are provided and will override the existing builtin assertions if the bignumber property is explicitly set as part of the assertion chain:

  • equal/equals/eq
  • above/gt/greaterThan
  • least/gte/greaterThanOrEqual
  • below/lt/lessThan
  • most/lte/lessThanOrEqual

The above methods have the following signature: (value, dp, rm). Where dp is an optional argument which specifies the number of decimal places to round each side of the comparison to (values are not rounded by default), while rm is an optional argument which specifies the rounding mode as supported by bignumber.js (defaults to BigNumber.ROUND_HALF_UP).

A set of additional assertion properties is also provided:

  • finite
  • integer
  • negative
  • zero

Values can be instances of number, BigNumber or string which can be converted into a valid number. Only BDD style (expect or should) assertions are supported.

Examples

Methods:

var result = new BigNumber('100000000000000000').plus(1);
var expected = '100000000000000001';
result.should.be.bignumber.equal(expected);
expect(result).to.be.bignumber.at.most(expected);
'1000'.should.be.bignumber.lessThan(2000);

Methods with rounding:

var BigNumber = require('bignumber.js');
(100.343).should.be.bignumber.equal(100.341, 2);
(100.349).should.be.bignumber.equal(100.341, 2, BigNumber.ROUND_DOWN);

Properties:

(100 / 0).should.not.be.finite;
expect(10).to.be.integer;
(-100).should.be.negative;
expect(1 - 1).to.be.zero;

License

MIT