Jest & Enzyme | Test PropTypes Function in componentDidMount

Question

I have this code in my component, that takes listUsers, as a required PropType func. I want to test that in the componentDidMount() , it should be called only once.

Component Code:

   static propTypes = {
    securityMode: PropTypes.string.isRequired,
    listUsers: PropTypes.func.isRequired
  };

  componentDidMount() {
    const { listUsers } = this.props;
    listUsers();
  }

    onCreateUserSucess= response => {
    this.setState({ isCreateUserModalOpen: false });
    const { listUsers, notify } = this.props;
    listUsers();
    this.closeCreateUserModal();
    notify({
      title: 'Created User',
      message: `User ${response.username} was added to group: ${response.group}`,
      status: STATUS.success,
      dismissible: true,
      dismissAfter: 3000
    });
  };

I get an error, saying that spyOn can only be appliead to functions. Can someone help me to test the. componentDidMount and onCreateUserSucess . I even tried to mock the functions but I always get failings.

Answer 1

Testing componentDidMount is pretty simple. Let's suppose that the component you created above is called UsersDisplayer .

class UsersDisplayer extends Component {
   constructor(props) {
      // ...
   }

   // The code above goes here.
}

In order to test whether the listUsers function runs or not, you should do something similar to this:

// Import React, shallow and UsersDisplayer at the top.

describe('<UsersDisplayer />', () => {
   let usersDisplayerWrapper;
   let listUsers;

   beforeEach(() => {
      listUsers = jest.fn();

      usersDisplayerWrapper = <UsersDisplayer listUsers={listUsers} />;
   });

   describe('componentDidMount', () => {
      it('calls listUsers props function', () => {
          // The `componentDidMount` lifecycle method is called during the rendering of the component within the `beforeEach` block, that runs before each test suites.
         expect(listUsers).toHaveBeenCalled();
      });
   });

   describe('onCreateUserSucess', () => {
      it('calls listUsers props function', () => {
         // Create a dummy `response` data that will be passed to the function.
         const response = {
            username: 'username',
            group: 'group'
         };

         // Simply just call the function of the instance.
         usersDisplayerWrapper.instance().onCreateUserSucess(response);

         expect(listUsers).toHaveBeenCalled();
      });
   });
});