Unit test form submission with data using react testing library

Question

I have a react component with a form. I want to unit test (using jest and RTL) if form gets submitted with correct data. Here are my component and unit test method:

Component:

class AddDeviceModal extends Component {
  handleOnSave(event) {
    const { deviceName } = event.target;
    const formData = {
      deviceName: deviceName.value,
    };
    this.props.onSave(formData);
  }

  render() {
    return (
      <Form onSubmit={this.handleOnSave}>
        <Form.Label>Device Name</Form.Label>
        <Form.Control name="deviceName" placeholder="Device Name" required />
        <Button type="submit">Save Device</Button>
      </Form>
    );
  }
}

Unit Test:

it("Test form submit and validation", () => {
  const handleSave = jest.fn();
  const props = {
    onSave: handleSave,
  };
  render(<AddDeviceModal {...props} />);
  const deviceNameInput = screen.getByPlaceholderText(/device name/i);
  fireEvent.change(deviceNameInput, { target: { value: "AP VII C2230" } });
  fireEvent.click(getByText(/save device/i));
});

However, in handleOnSave(), I get error as deviceName is undefined. For some reason, it is not able to get the textbox value from event.target. Am I doing something wrong in above code? Needed help in fixing this issue.

Answer 1

The problem you have it with trying to access the input directly from event.target. You should access it from event.target.elements instead: https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement/elements.

function handleOnSave(event) {
  event.preventDefault();
  const { deviceName } = event.target.elements;
  const formData = {
    deviceName: deviceName.value
  };

  // this will log the correct formData even in tests now
  console.log(formData);
  this.props.onSave(formData);
}

And here is your test:

it("Test form submit and validation", () => {
  const { getByPlaceholderText, getByText } = render(<App />);
  const deviceNameInput = getByPlaceholderText(/device name/i);

  fireEvent.change(deviceNameInput, { target: { value: "AP VII C2230" } });
  fireEvent.click(getByText(/Save Device/i));
});

I created a codesandbox where you can see this in action: https://codesandbox.io/s/form-submit-react-testing-library-45pt8?file=/src/App.js