Returns a wrapper around the node at a given index of the current wrapper.
index(Number): A zero-based integer indicating which node to retrieve.
ShallowWrapper: A new wrapper that wraps the retrieved node.
const wrapper = shallow(<MyComponent />);
expect(wrapper.find(Foo).at(0).props().foo).to.equal('bar');.get(index) => ReactElement- same, but returns the React node itself, with no wrapper..first() => ShallowWrapper- same as at(0).last() => ShallowWrapper