chai-bn

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Chai assertions for comparing arbitrary-precision integers using the bn.js library. Forked from chai-bignumber, which uses the bignumber.js library.

Installation

npm install --save-dev chai-bn

Usage

const chai = require('chai');
const BN = require('bn.js');

// Enable and inject BN dependency
chai.use(require('chai-bn')(BN));

Assertions

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

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

A set of additional assertion properties is also provided:

  • negative
  • zero

Actual values (i.e. the values being asserted) must be instances of BN. Expected values (i.e. the values the actual value is expected to match) may be instances of either BN or string which can be converted into a valid number. This is a key difference with chai-bignumber, which automatically converts JavaScript numbers and strings to BigNumber instances for both actual and expected values.

Only BDD style (expect or should) assertions are supported.

Examples

Methods:

const actual = new BN('100000000000000000').plus(new BN('1'));
const expected = '100000000000000001';

actual.should.be.a.bignumber.that.equals(expected);
expect(actual).to.be.a.bignumber.that.is.at.most(expected);
(new BN('1000')).should.be.a.bignumber.that.is.lessThan('2000');

Properties:

(new BN('-100')).should.be.a.bignumber.that.is.negative;
expect(new BN('1').sub(new BN('1'))).to.be.a.bignumber.that.is.zero;

Some Chai properties (e.g. the that.is chain) have no effect other than increasing readability, and can be dropped if less verbosity is desired.

License

MIT