This test should fail if the function returns the original array (instead of a copy of the original array).

The current test checks only if both the original array and the returned array contain identical elements.
In order to validate the returned array is a different array, we need an additional check.

Can you implement this additional check?

Decimal numbers in most programming languages (including JS) are internally represented in "floating point number" format. Floating point arithmetic is not exact. For example, the result of 46.5678 - 46 === 0.5678 is false because 46.5678 - 46 only yield a value that is very close to 0.5678. Even changing the order in which the program add/subtract numbers can yield different values.

So the following could happen

 expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.805 ); // This fail
 expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.8049999999999997 ); // This pass
 expect( 0.005 + 0.6 + 1.2 ).toEqual( 1.8049999999999997 ); // This fail
 console.log(1.2 + 0.6 + 0.005 == 1.805); // false
 console.log(1.2 + 0.6 + 0.005 == 0.005 + 0.6 + 1.2); // false

Can you find a more appropriate way to test a value (that involves decimal number calculations) for equality?

Suggestion: Look up

• Checking equality in floating point arithmetic in JavaScript
• Checking equality in floating point arithmetic with Jest

That was interesting. Thank you.
And hope I got it right.

Line 33 does not quite check if the function returns a copy of the original array.

If the input does not involve decimal numbers, toEqual() is better.

All integers in the interval [-Number.MAX_SAFE_INTEGER, Number.MAX_SAFE_INTEGER] can be represented precisely.