Cypress E2E Mock GraphQL Subscription as Query

Is there a way to mock a subscription from GraphQL? I only need to return some data once. So pretty much instead of a subscription have a GET query.

I did have a look into the Cypress-Documentation but I only saw something about queries and mutations.

Subscriptions use the wss instead of the https protocol and are not POST methods. Thus, I do not think it is possible to use the

cy.intercept('POST', 'http://localhost:3000/graphql', (req) => {...})

style of request mocking.

For the GraphQL requests, I am using the React Apollo library.

It is peculiar that I didn't find anything in this direction. I am new in E2E testing so maybe my thought process is wrong.

I am using Cypress v13.

There is an issue thread with a custom command here Mock websockets #2492 which apparently works for the author, and has 7 thumbs.

import { Server, WebSocket } from "mock-socket"

const mockGraphQlSocket = new Server(Cypress.env("GRAPHQL_WEB_SOCKET"))

Cypress.Commands.add("mockGraphQLSocket", mocks => {
  cy.on("window:before:load", win => {
    win.WebSocket = WebSocket
    mockGraphQlSocket.on("connection", socket => {
      socket.on("message", data => {
        const { id, payload } = JSON.parse(data)

        if (payload && mocks.hasOwnProperty(payload.operationName)) {
          mocks[payload.operationName](
            // Delegate the socket send call to the party owning the mock data since multiple calls might need to be made (for example to update multiple individual entries)
            data =>
              socket.send(
                JSON.stringify({
                  type: "data",
                  id,
                  payload: { errors: [], data }
                })
              ),
            payload.variables
          )
        }
      })
    })
  })
})

In the test

cy.mockGraphQLSocket({
    yourGraphQlQuery: (send, { uuids }) => {
      uuids.forEach(id => {
        send({
          yourGraphQlQuery: {
            ...yourMockData,
            id
          }
        })
      })
    }
  })