Reduce the set of matched nodes to the last in the set, just like .at(length - 1).
ShallowWrapper: A new wrapper that wraps the last node in the set.
const wrapper = shallow(<MyComponent />);
expect(wrapper.find(Foo).last().props().foo).to.equal('bar');.at(index) => ShallowWrapper- retrieve a wrapper node by index.first() => ShallowWrapper