Thanks for the suggestions, I have incorporated them.

https://www.youtube.com/watch?v=yPYxQQglBGM

The hardest parts seem to (0) understand the problem in a meaningful way, (1) to optimize the solution so long that it passes all tests without timeout.

What happens when the input starts with a blank (that was explicitly stated as possibility)?

There may be a missing test.

Should we not better round to the nearest integer, e.g. for numerical stability?

There is missing a test, because this solution ignores when the sum of elements is 0, maybe something like

@Test fun givenA0sum_returns0() {
assertEquals(0, EqualSidesOfAnArray([1,-1])
}