trouble a brewin' in some reactive waters, redux!

TodosList.jsx

import React from 'react';
import { connect } from 'react-redux';

export class TodosList extends Component {
  static propTypes = {
    todos: PropTypes.arrayOf(todoPropTypes).isRequired,
    isLoading: PropTypes.bool.isRequired,
    hasErrored: PropTypes.bool,
    dispatch: PropTypes.func.isRequired,
  };

  randomlyHideTodos = () => {
    const toggledTodos = this.props.todos.map(todo => {
      if (Math.random() > 0.5) {
        todo.hidden = true;
      }
      return todo;
    }
    this.props.dispatch(updateTodos({ todos: toggledTodos }));
  };

  render() {
    return (
      <ul>
        {this.props.todos.map(todo =>
          <Todo
            key={todo.id}
            {...todo}
          />
        )}
      </ul>
    );
  }
}

const mapStateToProps = state => {
  return {
    todos: state.todosReducer.todos,
    isLoading: state.todosReducer.isLoading,
    hasErrored: state.todosReducer.hasErrored,
  };
};

export default connect(mapStateToProps)(TodosList);

TodosList.test.js

import { shallow, mount } from 'enzyme';
import configureStore from 'redux-mock-store'
import { TodosList } from 'components/TodosList';

import { mockTodosData } from '__mocks__/todos';

describe('TodosList Component', () => {
  let wrapper;
  const middlewares = [];
  
  beforeEach(() => {
    wrapper = shallow(
      <TodosList
        todos={mockTodosData}
        hasErrored={false}
        isLoading={false}
        dispatch={jest.fn()}
      />
    );
  });
  it('can randomly hide todos and dispatch result to redux', () => {
    const visibleTodos = 10;  // mock data has 10 hidden = false todos
    wrapper.instance().randomlyHideTodos();
    const newVisibleTodos = wrapper.instance().props.todos.reduce((a, b) => { b.hidden ? a + 1 : a }, 0);
    expect(newVisibleTodos).toBeLessthan(visibleTodos);
  });
});