chai.js has cool API that allows for checking if two values (including floats) are close to each other.
For example, you can't realy check

expect(0.1+0.2).to.be(0.3)

because there is always rounding error in floating point calculation.
So instead in chai you write

let EPS = 1e-5;
expect(0.1+0.2).to.be.closeTo(0.3, EPS)

This function is oneliner, so this totaly fits "minimalistic" idea.

I know that I can use something like

expect(abs(f1-f2)).to.be.below(EPS)

but this is not very intuitive for reader that my intention is just check that f1 and f2 are just close to each other.