Cypress fixture returns an object that somehow is not an instanceof Object

Current behavior

cy.fixture("example.json").then(fixture => console.log(fixture instanceof Object))

Logs false

console.log(require("../../fixtures/example.json") instanceof Object);

Logs true

This is a problem because we use Immer to mutate state but it doesn’t work on the fixture data, breaking our app in Cypress tests.

Desired behavior

cy.fixture("example.json").then(fixture => console.log(fixture instanceof Object))

Logs true

Test code to reproduce

https://github.com/jordyvandomselaar/Cypress-fixture-no-instanceof-object-bug

Versions

1. “cypress”: “^6.5.0”,
2. MacOS Catalina 10.15.6

[jennifer-shehane]

it('cy.fixture() - load a fixture', () => {
  cy.fixture("example.json").then((fixture) => {
    // logs false
    console.log("Cypress Fixture", fixture instanceof Object)
  })

  // logs true
  console.log("Require Fixture", require("../../fixtures/example.json") instanceof Object);
  
  // logs true
  console.log("Plain Object", {"key": "value"} instanceof Object);
})

The code for fixtures can be found here: https://github.com/cypress-io/cypress/blob/develop/packages/server/lib/fixture.js#L39:L39

For now I would recommend requiring the fixtures as you showed where it will be instanceof Object.

[bahmutov]

@jordyvandomselaar can I ask how you are using the object loaded from the fixture? Do you pass it to the application somehow? In the repo you provided you just have the spec code like

context('Files', () => {
  it('cy.fixture() - load a fixture', () => {
      cy.fixture("example.json").then(fixture => console.log(fixture instanceof Object))

      console.log(require("../../fixtures/example.json") instanceof Object);
      console.log({"key": "value"} instanceof Object);
  })
})

Which to me is fine, the above workarounds are enough. I would love to fix the application example if you can provide one.