Improve stacktrace

[Conaclos]

Hi!

I have often difficulties to locate which assertion fails in my unit tests. Let's just take an example to illustrate this.

Usually my unit tests have several assertions, such as:

import test from "oletus"
test("example", t => {
    t.ok(true)
    t.ok(false)
})

The reported location is a bit evasive:

$ oletus test.js
x error
test.js:2

We don't know whether it is the first or the second assertion that failed. It could be nice to get the line where the assertion failed:

$ oletus test.js
x error
test.js:4

However I don't see how to get this location in a reliable way. Indeed: we do not know which assertion library is used and which test pattern are used. The current approach (reporting the test location) seems more reliable.

A possible approach could be to report a reliable location (the location currently reported) and an unreliable location:

$ oletus test.js
x example
test.js:2
test.js:4

However, I am not convinced by this. Have you some thoughts?