How to mock file upload or file object in jest?

Question

I want to mock file-upload with jest to test my apollo-server, I use graphql to define and pass data. But I find it is very difficult to mock file object in jest. I search with google and spend lots of time, but still can't find an answer.

As some guy suggest, I use this method. https://gist.github.com/josephhanson/372b44f93472f9c5a2d025d40e7bb4cc,

but when I see the return of the back-end, it tells me createreadstream is not a function.

This is the graphql I defined.

type Mutation{
changeFlowStatus(flowLog: FlowLogInput!, files: [Upload!], newStatus: Status): FlowLog
}
resolvers{
Upload: GraphQLUpload,
Mutation: {
  changeFlowStatus:
}

This is the jest part.

    //changeFlowStatus
    var size = 1024 * 1024 * 2;
    var mock = new MockFile();
    const file = mock.create("pic.jpg", size, "image/jpeg");
    const changeFlowStatus = await toPromise(
      graphql({
        query: CHANGE_FLOW_STATUS,
        variables: {
          flowLog: { reflowId: reflowId, timestamp: '1562716800', comment: 'flowLog_comment', title: 'flowLog_title' },
          files: [file],
          newStatus: 'SP_RECEIVED',
        },
        context: {
          useMultipart: true,
        },
      }),
    );

file is the object I create with the class mentioned above.

My expectation is simple, mock a file-upload process or file object with jest. Thanks.

Answer 1

I suppose you use apollographql, graphql-upload and jest.js, here is a integretion test for file upload:

it('should upload file correctly', async () => {
    const body = new FormData();
    body.append(
      'operations',
      JSON.stringify({
        query: `
          mutation ($file: Upload!) {
            singleUpload(file: $file) {
              code
              message
            }
          }
        `,
        variables: {
          file: null,
        },
      }),
    );

    const filename = '15625760447371547012340909WX20190108-124331.png';
    body.append('map', JSON.stringify({ 1: ['variables.file'] }));
    body.append('1', fs.createReadStream(path.resolve(__dirname, `./files/${filename}`)));
    const json = await fetch('http://localhost:4000', { method: 'POST', body }).then((response) => response.json());
    // logger.debug('upload testing#1', { arguments: { json } });
    expect(json).toEqual(
      expect.objectContaining({
        data: {
          singleUpload: {
            code: expect.any(Number),
            message: expect.any(String),
          },
        },
      }),
    );
  });

See Github example repo