How can I unit test Graphql Upload in api using Vitest

I wrote a test which creates a Venue with attachments property which is of Graphql Upload type. But when I try to run the test, it fails with error "message": "Variable \"$attachments\" got invalid value { fieldName: \"1\", filename: \"valid-image.png\", mimetype: \"image/png\", encoding: \"7bit\" } at \"attachments[0]\"; Upload value invalid." basically Upload value invalid.

In backend the attachments is structure like that

{
  fieldName: '1',
  filename: 'Screenshot 2023-09-05 193500.png',
  mimetype: 'image/png',
  encoding: '7bit',
  createReadStream: [Function: createReadStream]
}

Unit test

it("should create a venue with valid attachments", async () => {
    const imagePath = join(__dirname, "test-files", "valid-image.png");
    const variables = {
      organizationId: orgId,
      name: `Test Venue ${faker.string.alphanumeric(5)}`,
      description: "Test venue with valid attachments",
      capacity: 50,
      attachments: [
        {
          fieldName: "1",
          filename: "valid-image.png",
          mimetype: "image/png",
          encoding: "7bit",
          createReadStream: () => createReadStream(imagePath),
        },
      ],
    };

    const result = await mercuriusClient.mutate(Mutation_createVenue, {
      headers: { authorization: `bearer ${authToken}` },
      variables,
    });

    console.log('result is ', result);
   
  })

I have never tested FileUpload so I'm not sure whether I'm correctly testing it or not.

Any help would be appreciated.