isVueInstance is deprecated and will be removed in future releases

I have checked https://vue-test-utils.vuejs.org/api/wrapper/#isvisible and they say:

Assert Wrapper is Vue instance.

So the final thing would be:

it('is instantiated', () => {
    expect(wrapper).toBeTruthy();
  });

Here's how to rigorously check VueInstance

https://github.com/vuejs/vue-test-utils/blob/2d6b49780c7e1d663b877ddf5d6492ed7b510379/packages/test-utils/src/wrapper.js#L400

it('is instantiated', () => {
    expect(wrapper.vm).toBeTruthy();
});