openzeppelin / chai-bn

Chai assertions for comparing arbitrary-precision integers using the bn.js library

chai-bn

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

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 = 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

chai-bn's Issues

Add override for closeTo

We should provide a way to test for almost-equality: this is very useful when dealing with time, where some sort of tolerance is required.

See chai.closeTo.

Consider submitting TS types to DefinitelyTyped

TS types were provided by #10

Hoping that someone can submit these to Definitely Types.

I am not sure as to the etiquette of doing this for a Repo to which I am not an approver. So posting here.

Testing arrays of big numbers

Chai's members can be used to test that an array contains certain values, as determined by strict equality or optionally deep equality.

Neither of those is appropriate to test arrays of big numbers (although deep equality works, it isn't ideal). We could maybe make the bignumber property modify members to compare values using bignumber equality?

On the other hand, this same issue shows up with many other Chai assertions, like oneOf...

Change addProperty to overwriteProperty

https://github.com/ZeppelinSolutions/chai-bn/blob/4c036a28bd5b5b3e7273199b9520ce788ab1a51d/chai-bn.js#L118

https://github.com/ZeppelinSolutions/chai-bn/blob/4c036a28bd5b5b3e7273199b9520ce788ab1a51d/chai-bn.js#L131

See overwriteProperty.

Consider adding default value for BN instance

https://github.com/ZeppelinSolutions/chai-bn/blob/1900f60a9d5fbba3d44c755e24b5efe2f81d3a1d/chai-bn.js#L1

We could add a default value of BN = require('bn.js'). What do you think? Coupled with #3 it works out nicely I think.

Add proper peerDependencies

Both Chai and BN should be peerDependencies.

Types for this package

$ npm i --save-dev @types/chai-bn
npm ERR! code E404
npm ERR! 404 Not Found - GET https://registry.npmjs.org/@types%2fchai-bn - Not found

Are there any plans to add types?

Use stricter type checking

The isBN function is implemented with duck typing and it should only use the stricter instanceof.

https://github.com/ZeppelinSolutions/chai-bn/blob/4c036a28bd5b5b3e7273199b9520ce788ab1a51d/chai-bn.js#L15-L19