How to (can i?) load Cypress fixture inside intercept based on request data?

Question

I have a bunch of fixtures generated by the backend, and named based on the hash of the request body. I am trying to find a way to load fixtures dynamically based on the sent request, something like this:

cy.intercept('POST', '**/login', (req) => {
    const hash = md5(req.body);
    cy.fixture(`${hash}.json`).then(data => {
        req.reply(res => {
            res.statusCode = data.statusCode;
            res.body = data.body;
        })
    })
}).as('response');

cy.visit("/login");

cy.get('input[name="email"]').type('test@email.com');
cy.get('input[name="password"]').type('wrongpassword');
        
cy.contains('button', 'Login').click();

cy.wait('@response');

cy.contains('Invalid credentials.');

But every time I try to load a fixture inside an intercept, I get the following error:

The following error originated from your test code, not from Cypress.

  > A request callback passed to cy.intercept() threw an error while intercepting a request:

Cypress detected that you returned a promise from a command while also invoking one or more cy commands in that promise.

The command that returned the promise was:

  > cy.wait()

The cy command you invoked inside the promise was:

  > cy.fixture()

Is there any way, I could possibly load fixtures dynamically based on something inside the request?

Answer 1

You can just read the fixture first

cy.fixture('login_incorrect.json').then(data => { // may not need it, but in case...

  cy.intercept('POST', '**/login', (req) => {
    const body = JSON.parse(req.body);
    if(body.password === 'wrongpassword') {
      req.reply(res => {
        res.statusCode = data.statusCode;     // data = closure from above
        res.body = data.body;
      })
    } else {
      // load a different fixture based on something, etc.
    }
  }).as('response');

})

---

Combined fixture

{
  "put-first-hash-here": { 
    statusCode: ...,
    body: ...
  },
  "put-second-hash-here": { 
    statusCode: ...,
    body: ...
  },
}

Test

cy.fixture('combined.json').then(data => { 

  cy.intercept('POST', '**/login', (req) => {
    const body = JSON.parse(req.body);
    const hash = md5(req.body);
    if(body.password === 'wrongpassword') {
      req.reply(res => {
        res.statusCode = data[hash].statusCode;
        res.body = data[hash].body;
      })
    } 
  }).as('response');

})