Wrong place in the script is reported for failed assertions

[andrewslotin]

If an assertion fails inside a function call, the place where this function was called is reported instead of where the failing assertion is.

Here is the minimal script to reproduce the issue:

import { expect } from "https://jslib.k6.io/k6-testing/0.6.1/index.js";

export default function () {
  doTest();
}

function doTest() {
  expect(2 + 2).toBe(5);
}

When executed, the test result points to line 4 where doTest() is called instead of line 8 where the failing .toBe() assertion is:

k6 run script.js
// …
ERRO[0000] test aborted:

   Error: expect(received).toBe(expected)
      At: script.js:4:9

Expected: 5
Received: 4

Filename: test.js
    Line: 4

This makes it complicated to figure out what went wrong if a function contains multiple similar checks, e.g., validates the presence of several elements on the page.

[allansson]

I changed how we extract this information in #61. I tested the provided script in it and I got line 8 instead of 4, so it seems to fix the issue.