bn-chai

bn-chai extends Chai with assertions about bn.js decimals.

Installation

npm install -s bn-chai

Setup

var chai = require('chai');
var expect = chai.expect;
var BN = require('bn.js');
var bnChai = require('bn-chai');
chai.use(bnChai(BN));

Usage

When comparing two bn.js decimals bn1 and bn2, instead of doing:

expect(bn1.eq(bn2)).to.be.true;

You can do this instead:

expect(bn1).to.eq.BN(bn2);

This plugin is also handy when comparing a bn.js decimal to an inline constant, so instead of writing:

expect(bn1.eq(new BN('1'))).to.be.true;

You can simply write:

expect(bn1).to.eq.BN(1);

Which is simpler and more readable.

Assertions

eq

Asserts that the target is equal to the given object.

expect(new BN('1')).to.eq.BN(1);
expect(new BN('1')).not.to.eq.BN(0);

lt

Asserts that the target is less than the given object.

expect(new BN('0')).to.be.lt.BN(1);
expect(new BN('1')).not.to.be.lt.BN(1);

lte

Asserts that the target is less than or equal to the given object.

expect(new BN('0')).to.be.lte.BN(1);
expect(new BN('1')).to.be.lte.BN(1);
expect(new BN('2')).not.to.be.lte.BN(1);

gt

Asserts that the target is greater than the given object.

expect(new BN('1')).to.be.gt.BN(0);
expect(new BN('1')).not.to.be.gt.BN(1);

gte

Asserts that the target is greater than or equal to the given object.

expect(new BN('1')).to.be.gte.BN(0);
expect(new BN('1')).to.be.gte.BN(1);
expect(new BN('1')).not.to.be.gte.BN(2);

negative

Asserts that the target is negative.

expect(new BN('-1')).to.be.negative;
expect(new BN('1')).not.to.be.negative;

even

Asserts that the target is even.

expect(new BN('2')).to.be.even;
expect(new BN('1')).not.to.be.even;

odd

Asserts that the target is odd.

expect(new BN('1')).to.be.odd;
expect(new BN('2')).not.to.be.odd;

zero

Asserts that the target is equal to 0.

expect(new BN('0')).to.be.zero;
expect(new BN('1')).not.to.be.zero;

Mixing BN, numbers and strings

You can mix BN with numbers and strings freely:

expect(new BN('1')).to.eq.BN(new BN('1'));
expect(new BN('1')).to.eq.BN('1');
expect(new BN('1')).to.eq.BN(1);

expect('1').to.eq.BN(new BN('1'));
expect('1').to.eq.BN('1');
expect('1').to.eq.BN(1);

expect(1).to.eq.BN(new BN('1'));
expect(1).to.eq.BN('1');
expect(1).to.eq.BN(1);

Executing example tests

Example unit tests making use of this plugin can be executed by running the following commands:

cd test
npm run test; npm run failTest