Enzyme: Cannot convert undefined or null to object.

[ErrorPro]

Hi. I am using Jest with Enzyme. I have a component wrapped by few components(Provider, Intl, Relay). When i try to render the component with render function and then call .toMatchSnapshot it works perfect. But when i call mount instead of render it fails. The stack trace is:

TypeError: Cannot convert undefined or null to object

  at Object.<anonymous> (__tests__/common/Header/Header2.test.js:54:76)
  at handle (../node_modules/worker-farm/lib/child/index.js:41:8)
  at process.<anonymous> (../node_modules/worker-farm/lib/child/index.js:47:3)
  at emitTwo (../events.js:87:13)
  at process.emit (../events.js:172:7)
  at handleMessage (../internal/child_process.js:686:10)
  at Pipe.channel.onread (../internal/child_process.js:440:11)

The reason why i am calling mount that i need set props to the component.
Perhaps the problem is not in enzyme but in worker-farm lib. Anyway any help will be appreciated.

[andrychernysh]

Hi! I have the same problem

[ljharb]

Can you share the test code?

[ErrorPro]

@ljharb

  const store = configureMockStore()({
    form: {},
    theme: {},
  });
  const Container = Relay.createContainer(HeaderContainer, {
    fragments: {
      viewer: () => Relay.QL`
        fragment on Viewer {
          ${HeaderContainer.getFragment('user')}
        }
      `,
    },
  });
  const mockViewer = {
    ...notification,
    userProfile: {
      photoFile: {},
      account: {},
      impersonator: {},
      sexDictionary: {},
    },
    notificationsQuantity: 1,
    messagesQuantity: 2,
    adminMessagesQuantity: 3,
  };

  const instance = mount(
    <Provider store={store}>
      <IntlProvider
       key={'ru'}
       locale={'ru'}
       messages={[]}>
        <RelayMockRenderer
          render={() => <Container viewer={mockViewer} />}
        />
      </IntlProvider>
    </Provider>
  );
  console.log(toJson(instance))
  expect(toJson(instance)).toMatchSnapshot();

[ljharb]

Which line corresponds to __tests__/common/Header/Header2.test.js:54?

[ErrorPro]

the last one expect(toJson(instance)).toMatchSnapshot();

[ljharb]

That implies something wrong with the toMatchSnapshot call - is it not expected to take arguments? How is it being bootstrapped?

[ErrorPro]

There is mock for files(svg, png). Everything else is just basic. As i said it works with render but doesn't with mount.

[ljharb]

What's the implementation of IntlProvider look like? Where's worker-farm come in?

[ErrorPro]

import { IntlProvider } from 'react-intl'; I don't know where worker-farm comes in. I didn't find in my project where it is being called. I guess it's called by some library.

[cettoana]

Hi, maybe I have the same problem
and here is the stack trace

TypeError: Cannot convert undefined or null to object

      at Object.<anonymous> (src/scripts/components/__tests__/Panel.jest.js:32:134)
      at handle (node_modules/worker-farm/lib/child/index.js:41:8)
      at process.<anonymous> (node_modules/worker-farm/lib/child/index.js:47:3)
      at emitTwo (events.js:106:13)
      at process.emit (events.js:191:7)
      at process.nextTick (internal/child_process.js:752:12)
      at _combinedTickCallback (internal/process/next_tick.js:67:7)
      at process._tickCallback (internal/process/next_tick.js:98:9)

[ljharb]

Might be a jest thing. What version of jest, and do you have any mocks set up?

[john-hu]

Hi, same here. My jest version is 18.1.0.

The account list is not null or undefined The exception happens to the second line of the code:

        console.log(accountList);
        expect(toJSON(accountList)).toMatchSnapshot();

[ljharb]

where does toJSON come from?

[john-hu]

it's from https://www.npmjs.com/package/enzyme-to-json ..

BTW, ErrorPro's example also has toJSON....

[john-hu]

The error message is:

    TypeError: Cannot convert undefined or null to object

      at Object.<anonymous> (__tests__/container/list/AccountsList.test.js:105:89)
      at process._tickCallback (internal/process/next_tick.js:103:7)

BTW, I will file another issue to enzyme-to-json and link both of them.

[ljharb]

Looks like this is an issue with jest, not enzyme.