Good one. With no parameters it is expected that an error occurs, because a selectors are used to get the container and play button. We can tell the test that we expect that error to occur, by replacing the line with expect(…).toThrow().
expect(() => manageCover.init()).toThrow();
For greater clarity, we can extract that function call out to a separate fnCall function.
const fnCall = () => manageCover.init();
expect(fnCall).toThrow();
Now that we have specified that no parameters is expected to throw, we have the opportunity to provide a better error message by updating the test to indicate the message that we want, so that we can update the code to provide that better error message.
However, we are more interested in just getting some basic tests out. So after the test with no parameters is passing, we can move on to a test where we give it some parameters.