Fixture returns outdated/false data

Current behavior:

Reading and writing fixtures seems to not work as expected (please let me know if this is my error). Across two different tests (within the same spec) the returned value from cy.fixture is outdated and should have been updated by a previous call to cy.writeFile. This looks to me like a caching issue?

Desired behavior:

It should always return the latest data from the fixture and not something outdated.

Steps to reproduce: (app code and test code)

1. Create a empty spec and paste the below code.
2. Run the spec and see the output in the dashboard.

describe('fixture', () => {
  it('step 1', () => {
    // Create the fixture first
    cy.writeFile("cypress/fixtures/test-temp.json", {
      id: 1,
      name: 'Step 1'
    });

    // Let's see the data, it should be fine
    cy.fixture("test-temp").then(data => cy.log(data));

    // Update the fixture again
    cy.writeFile("cypress/fixtures/test-temp.json", {
      id: 1,
      name: 'Step 2'
    });
  });

  it('step 2', () => {
    // Let's wait 5 seconds just to be sure
    cy.wait(5000);

    // The returned data is { id: 1, name: 'Step 1' }
    // Should be { id: 1, name: 'Step 2' }
    cy.fixture("test-temp").then(data => cy.log(data));
  });
});

Versions

Cypress 3.4.0 & 3.3.2 MacOS Mojave Chrome 75

UPDATE: No need to create 2 different tests, it also happens inside the very same test.

[jennifer-shehane]

So I asked the team about this. We are indeed caching the reference to the fixture to save memory. This was intended at the time, but is likely not a great solution now.

We likely need to rework this logic, to not use the cache when the file has been changed. We can detect that the file has changed by initially getting the SHA, compare if SHA has changed, otherwise use cache. Alternatively look at modifiedAt time of the file (if works on all platforms)

Workaround:

You can use cy.readFile() instead of fixture as this will not use the cacheing.

[x-yuri]

I don’t really see a case for changing fixtures. Fixtures is something prepared in advance and shouldn’t change. If you want to randomize test data, you need faker or something.

Change fixtures to match changes made by API requests? Do you even need fixtures in this case? To answer that question I need more details. What data you have in fixtures? What requests you make?

The bottom line is if you need to change fixtures, that’s most likely a sign you’re doing something wrong. Or so I think for now.