Mocking in tests.
Are you able to provide an example of testing the File upload mutations via the MockedProvider from react-apollo/test-utils?

I cannot get the mocks to match because the variable is a File, which I cannot add to the mock variables.

e.g. 
Assuming a simple File upload like this one named input 

https://github.com/jaydenseric/apollo-upload-client#file

```js
import gql from 'graphql-tag';
import { MockedProvider } from 'react-apollo/test-utils';
import { fireEvent, render } from '@testing-library/react';

import Input from '../Input';

export const IMAGE_UPSERT = gql`
  mutation ImageUpload($file: Upload!) {
    imageUpload(file: $file) {
      image {
        id
        alt
        src
      }
      success
    }
  }
`;
const mocks = [
  {
    request: {
      query: IMAGE_UPSERT,
      variables: {
        file: { path: 'juice.png' },
      },
    },
    result: {
      data: {
        imageUpload: {
          image: { id: 'image345==', alt: 'juice.png', src: 'juice.png' },
          success: true,
        },
      },
    },
  },
];

describe('Input', () => {
  it('uploads', async () => {
    const { container } = render(
      <MockedProvider mocks={mocks} addTypename={false}>
        <Input {...props} />
      </MockedProvider>
    );
    const file = new File(['(⌐□_□)'], 'juice.png', {
      type: 'image/png',
    });

    const fileEl = container.querySelector('input[type="file"]');
    Object.defineProperty(fileEl, 'files', {
      value: [file],
    });
    fireEvent.change(fileEl);
  });
});
```

This leads to an unmatched mutation

```
No more mocked responses for the query: mutation ImageUpload($file: Upload!) {
      imageUpload(file: $file) {
        image {
          id
          alt
          src
        }
        success
      }
    }
    , variables: {"file":{"path":"juice.png"}}
```

The variables actually passed to the client look like this

```js
{ variables:
       { file: File { path: 'juice.png' } },
```

Just curious if you've already got a solution that I'm just missing.

Thanks for any input!