Throw error when trying to set Cypress.config() for non-mutable config values

[jennifer-shehane]

Current behavior:

When trying to set Cypress.config() for non-mutable configurations which are ignored from inside of the tests, Cypress does not perform the action as expected and does not throw an error.

Example:

The test below passes, but Cypress does not indeed change the location of the screenshotsFolder, nor does it throw an error telling you that the screenshotsFolder was not set.

it('screenshots folder not settable', () => {
  Cypress.config('screenshotsFolder', 'cypress/screenshots/desktop')
  expect(Cypress.config('screenshotsFolder')).to.eq('cypress/screenshots/desktop')
  cy.screenshot('homepage_desktop')
})

Actual saved screenshot location

Related issues:

• Does not print full config: Cypress.config() does not return the complete configuration #509
• Trying to set screenshotsFolder: screenshotsFolder not working correctly  #1525

Desired behavior:

• Cypress should throw an error when trying to set non-mutable configuration values.
• Make list of all config values that are mutable vs non-mutable. Maybe add to documentation.

Versions

Cypress 3.1.5

[aurium]

Hi, i want to solve this issue.

I console.loged the extended state inside set() at setter_getter.coffee and the screenshotsFolder value was updated in it (as expected) using Cypress.config in a test. How can i know which key it can or can't change?

[jennifer-shehane]

Closing as Duplicate of #6407