Issues with Cypress Tests and Single Fetch in React Router v7

[tcov189]

Hello all,

We’re currently upgrading from Remix 2.8 to React Router v7 and have encountered an issue with our Cypress tests that appears to be related to the Single Fetch implementation.

In many of our test suites, we use cy.intercept to mock responses from POST requests and form submissions. Here's an example that would be in one of our tests that mocks an error state on a form submission:

cy.intercept("POST", `*account/search.data*`, {
  body: {
    result: "error",
    message: errorMessage,
  },
}).as("postSearch");

When v3_singleFetch is enabled, this test fails with the following error:
Error: Unable to decode turbo-stream response from URL

I assume this is because React Router expects the response to be in turbo-stream format.

We also use cy.request to fetch data from other routes for purposes like validating input options on pages. Here's an example:

cy.request({
  method: "GET",
  url: `categories.data`,
}).then((request) => {
  cy.visit("/products");

  const { categories } = request.body;
  for (const item of categories) {
    cy.get("#item-select option").contains(item.name);
  }
});

This test is now failing because categories is no longer defined.

So my questions are:

• Is there a utility or helper available to create or parse turbo-stream requests/responses for testing purposes?
• Alternatively, is there a recommended pattern for testing form submissions and route data when Single Fetch is enabled?

Thanks in advance for any guidance!

[brophdawg11]

There aren't any utilities exposed at the moment but if you want to open a Proposal I don't see why we couldn't expose some helpers alongside our testing utilities.

That said, for now, since it's just using https://www.npmjs.com/package/turbo-stream v2.4.1, you can probably get by just using that directly to encode/decode. At one point we upstreamed the code into the RR repo and made I think one very minor change (don't recall what offhand though) but chances are it won't impact your testing.