Enzyme mount() not rendering child components

I try to test a React component containing child components. This is not a unit test - I want to simulate a click on a subcomponent and check if the result is what I expect. My setup is (schematically) as follows:

<Board />
    <Row />
        <Card />

... where component Board contains multiple Row components and component Row contains multiple Card components (yes, it's a board game). When clicking a Card it should flip, displaying the image (yes, it's a memorygame). So I use Enzyme's mount() on the because I want to be able to select a childcomponent of the Board.

This is the relevant rendered HTML from Chrome Developer tools Inspector tab:

Note that the Board contains Rows that contain Cards, identified by their like-named classes.

I am able to select a Card:

expect(component.find("[data-id='6'] .class")).toBeDefined()

doesn't throw error but when I simulate a click on a Card I do get an error. This is my test:

import React from "react";
import { Board } from "../components/Board";
import { mount } from "enzyme";

let component;

beforeEach(() => {
    component = mount(<Board />);
    console.log(component.debug());
});

describe("Test the puzzle", () => {
    it("should show 1 turned card when clicked", () => {
        const button = component.find(".button");
        const card = component.find("div[data-id='7']");

        expect(button).toBeDefined();
        expect(card).toBeDefined();
        button.simulate("click");
        card.simulate("click");
    });
});

This gives the errors

● Test the puzzle › should show 1 turned card when clicked

    Method “simulate” is meant to be run on 1 node. 0 found instead.       

      44 |              expect(card).toBeDefined();
      45 |              button.simulate("click");
    > 46 |              card.simulate("click");
         |                   ^
      47 |      });
      48 | });
      49 | 

The debugging() output of the the Board shows a shallow mount: Board contains a Row but Row does not contain Cards:

<Board>
  <div className="container">
    <div className="board">
      <Row cards={{...}} onClick={[Function: onClickCard]} updateCardReference={[Function: updateCardReference]}>
        <div className="row" />
      </Row>

So that leads me to believe there's nothing wrong with my selecting DOM elements but Enzyme's mount() is doing a shallow mount instead.

What do you think?

"react": "^16.13.1",
"react-dom": "^16.13.1",
"@testing-library/jest-dom": "^5.11.5",
"enzyme": "^3.11.0",
"enzyme-adapter-react-16": "^1.15.5",