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chai-ethers-bn

Chai assertions for comparing arbitrary-precision integers using the BigNumber library from ethers. Forked from chai-bn.

Installation

npm install --save-dev chai-ethers-bn

Usage

import chai from 'chai';
import { BigNumber } from 'ethers';
import chaiEthersBN from 'chai-ethers-bn';

// Enable and inject BN dependency
chai.use(chaiEthersBN());

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

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

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

Examples

Methods:

const actual = BigNumber.from('100000000000000000').plus(BigNumber.from('1'));
const expected = '100000000000000001';

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

Properties:

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

To make things shorter you can also use the alias bn:

actual.should.be.a.bn.that.equals(expected);

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