Feature proposal: enhance expectations so that they show similar to mocha runner

[SgtPooki]

Mocha shows failures in a very easy to read format where each expectation shows the following:

1. expected result
2. actual result
3. difference

3 could be challenging, but it should be trivial to update the expectation code to show the expected value and actual value given a particular path. Something like this for an expectation would be nice:

interface Expectation<T> {
  message?: (expected, actual) => string
  expectedValue: T,
  pathToActual: string[]
}

where

• Expectation['message'] would default to

const defaultFailureMsg = `Expected ${expected} but received ${actual} at path ${pathToActual}`

on failure and

const defaultSuccessMsg = `Correctly received expected value of ${expected} at path ${pathToActual}`

[SgtPooki]

Thoughts @lidel? @hacdias?

[SgtPooki]

Played with some type adjustments for this on https://github.com/ipfs-shipyard/pinning-service-compliance/tree/upgrade-expectations