"This is just an example of how you can write your own TDD tests - Expected: [2, 3, 3], instead got: [2, 3, 3] "
What the heck, there is something wrong with your test. Does this make sense. I will downvote this once i solve it.

I'm also getting a strange error, "✘ expected:<10> but was:<0>", looks like it's talking about some reference?

I wrote the solution in Java.