[@web/test-runner]: Logging complex (including circular) objects brings tests to a near-halt

[rschristian]

I'm running into an issue where wtr will slow to a near halt, usually timing out, upon encountering "complex" objects to log, which makes debugging tests considerably more difficult. Circular objects are sure to set it off (i.e., DOM nodes), but others with simply enough nesting will do it too. This also presents in the browser with --manual, I'm guessing due to something attempting to intercept all logs.

#1356 (comment) might be related and suggests this might be Mocha, but if so, are there any work arounds? Being able to quickly log a DOM node and other similarly "complex" objects to debug is a pretty crucial feature for my use, the current serializer, wherever it is, seems to really be struggling.

[rschristian]

The serialization seems to also be so slow as to cause significant issues with our tests that (unfortunately) require forms of await sleep(...); logging of any object at all is often taking upwards of 10-20ms, which is pretty non-representative.

[rschristian]

Running into this again today, this time, trying to log out Sinon calls. CPU hits 100% and Firefox tabs will crash. Very difficult to use.

[atjn]

+1 this is causing all my tests to timeout because I do the simple check expect(htmlElement1).to.be(htmlElement2);.

I have tested it some more and it seems to work with elements that are not part of the DOM. See the following example:

const p1 = document.createElement("p");
const p2 = document.createElement("p");
document.body.appendChild(p2); // <- this is what makes the test timeout
expect(p1).to.equal(p2);

The above test will timeout, but if you remove line 3, it will work as expected and return: AssertionError: expected <p></p> to equal <p></p>.

[devversion]

I'm also seeing this when printing complex class instances that have references back to the class instance. I wonder if it would make sense, or be sufficient to replace the custom replacer logic with e.g. https://www.npmjs.com/package/safe-stringify