Intercept gRPC support

[jstorm31]

We have Cypress tests for a web app with a gRPC backend API and would like to intercept API calls with cy.intercept. The interception works fine, but I'm struggling with defining response body so our grpc client accepts it. We use grpc-web client library.

There is cypress-protobuf plugin, but doesn't work out with neither our app nor cy.intercept. Therefore, we create the grpc messages directly and serialize it to binary representation.

import { SendFeedbackEmailResponse } from '../../grpc-client/v1/user_pb';

const message = new SendFeedbackEmailResponse();
message.setStatus(1);
const body = message.serializeBinary(); // Returns UInt8Array

cy.intercept('POST', `${Cypress.env('API_URL')}/SendFeedbackEmail`, {
   statusCode: 200,
   headers: {
      'content-type': 'application/grpc-web+proto',
   },
    body,
});

As I said, the intercept works fine, but the app fails on grpc client failing to decode the response. That implies the issue is in a combination of correct body representation and maybe content-type.

I wonder whether there are any folks that successfully use intercepts for grpc API calls or the Cypress team plans any built-in support for it. Thx 🙌

[seanmcquaid]

Curious here but did you ever end up solving this?? I am running into the same thing currently!

[jstorm31]

Well, no 😅. At the and we discoverd we would have to dig deep into the improbable grpc-web library we use and define the response format for intercept exactly the same way, so the application can understand it, which was not worth the time for our use case.

It may also work better for a different gRPC web client.

At our company, we plan to use gRPC more often in the future, which could lead to creating a plugin to Cypress, but as I said, it isn't worth the effort at the moment for us. 🤷‍♂️

[seanmcquaid]

It's all good, I figured I would at least ask! Unfortunately we are using grpc-web and we're running into the exact same issue currently at my company. We're also planning to use gRPC a lot more in the future so I will keep you posted if we end up going down a similar path and creating a plugin for this!

[Parsa-Sedigh]

@seanmcquaid did you make it work? I want to stub some of my grpc responses with a fixture, but I can't decode the response to decide whether that request should be stubbed or not.

[AmitLevinsky]

I'm also curious if you found a solution for your question? I'm working on E2E tests with mock data.
I managed to intercept the grpc request with cy.intercept and req.reply with headers and body but the response.message in the generated TS code is always null not matter what body is set in the req.reply of cy.intercept
we also using importable-grpc-web
Any thoughts why i'm getting response.message that is null all the time?

[jstorm31]

Nope, I didn't find any solution.