.to.deep.equal() with tolerance

I would like to use expect(a).to.deep.equal(b) to compare two JSON objects, but the objects contain floating-point numbers that are only roughly the same. Is there some way to compare those two objects with a tolerance when comparing numbers? i.e. when the algorithm compares numbers it will accept a difference of up to 0.001% or something like that.

[Turbo87]

@keithamus FWIW I implemented my first example as a chai plugin: https://github.com/Turbo87/chai-roughly

it’s using my branch from https://github.com/chaijs/deep-eql/pull/10 underneath

[keithamus]

You can use closeTo individual properties and assert that they are close to a number, within a given delta. For example:

expect(1.5).to.be.closeTo(1, 0.5);

Deep Equal will currently only compare like for like, but the plan with #644 is to get it to offer that kind of flexibility, so you could write something like:

expect({
  foo: 1.5
}).to.deep.equal({
  foo: expect.to.be.closeTo(1, 0.5)
});

While your example would solve your specific use case, I’m not sure it would be generic enough to put into chai core. Having said that, when #644 is done there could be the scope for you to create a plugin to modify how deep.equal compares values - so your example code would be possible then.