Function stringifyException

src/tests/frontend/runner.js:6–24

(exception)

// async function for some bizarre reason, so the async function is wrapped in a non-async function.
$(() => (async () => {
  const stringifyException = (exception) => {
    let err = exception.stack || exception.toString();

    // FF / Opera do not add the message
    if (!~err.indexOf(exception.message)) {
      err = `${exception.message}\n${err}`;
    }

    // <=IE7 stringifies to [Object Error]. Since it can be overloaded, we
    // check for the result of the stringifying.
    if (err === '[object Error]') err = exception.message;

    // Safari doesn't give you a stack. Let's at least provide a source line.
    if (!exception.stack && exception.sourceURL && exception.line !== undefined) {
      err += `\n(${exception.sourceURL}:${exception.line})`;
    }

    return err;
  };

  const customRunner = (runner) => {
    const stats = {suites: 0, tests: 0, passes: 0, pending: 0, failures: 0};