I think it is because you used console.log, not that it should be a problem, but it isn't appropriate for the solution. Check the question again and read what it is asking for. Your hint lies in the task description.

I feel that the property names should be listed. It is pretty typical and expected that the animal's name property is "name", but this is a 8 kyu kata. I actually console.log()'d the Animal class to double-check.

It wasn't descriptive enough. I didn't know to expect the input to be an array until after I passed many tests.

Another issue is that I wasn't sure if I was looking for interruptions in sequences. Knowing that it can be shuffled made sense once I started seeing tests (only after hitting Submit) having a jumble on numbers. That's when I realized I'm supposed to reorder them.

I have no idea how to rate this Kata on difficulty because depending on what it is asking for, the difficulty varies. You can see how the vagueness can make that even more difficult.

Spaces are being ignored in my strings. If I concat like this: 'foo ' + ' bar', the spaces won't show up. It works in my developer console.

It's a bug in the test code. If you want a challenge, read the error carefully. It gives you information needed to pass the kata's bug.

I'm experiencing this too. This is also technically a spoiler.

One solution returned the number as a string. I think the data type should remain a number since that is what you would expect from a function like this. A string shouldn't pass because it isn't even really a number anymore.