setState() method call when using mocha + enzyme is not affecting the state of component

When I use setSate() method on compiled component, the state is not being set. The control is taking the state from the production code and not the state assigned from the test. Find the code below.

const wrapper = mount(<BookFlight />
    wrapper.setState({ cabins: {
          fields: [
            {
              label: 'Economy',
              value: 'econ',
              name: 'cabin',
              type: 'radio'
            },
            {
              label: 'Business',
              value: 'business',
              name: 'cabin',
              type: 'radio'
            },
            {
              label: 'First',
              value: 'first',
              name: 'cabin',
              type: 'radio'
            }
          ]
        }})
        expect(wrapper.state().cabins.fields.length).toBe(3)