The tests aren't checking that the overriden operations return actually random values.

for (let i = 0; i < random(100, 200); i++)

This is not a correct way to randomize the number of loop iterations. And the number of tests shouldn't be random at all, tbh.

The sample tests include every operation that should be supported

The result of the in operator should be random
Result should be random: expected 0.012345679012345678 to be at least 0.2

What is this then?