Lifetime of intercept

[Cito]

The documentation for intercept() should explain the following things:

• How long is the lifetime of an intercept() command? (It should be documented that the effect is reset before each test.)
• What happens when you execute multiple intercept() commands? Does the second one replace the first? Or are they "stacked" on each other?
• Is it possible to manually remove the effect of all intercept() commands within a test (or the effect of the last one if they are "stacked")?

Here are two use cases that I had in mind:

• Having an intercept() in beforeEach() that should not be effective or altered just for one or a few of the tests.
• I want to simulate a temporary server error.
  • Create an intercept() that returns a status code of 500.
  • Try to execute a function in the UI that needs the server, e.g. a login.
  • Check that the UI reacts properly and shows a nice error message to the user.
  • "Repair" the server by removing the effect of the last intercept()
  • Try to execute the same function.
  • Check that the UI now does what is expected and there is no more error message.

For the second use case, I could create a dynamic intercept that only returns the error on the first try and otherwise passes the real result from the server. But it seems more complicated to me.

[Cito]

Here is the solution with the dynamic intercept.

The following function can be used to simulate a given number of server errors (by default, one error only).

Cypress.Commands.add('simulateNetworkError', (calls = 1, statusCode = 500) => {
  cy.intercept(
    { method: 'POST', url: '/graphql' },
    (req) => {
      if (calls) {
        req.reply({ statusCode });
        --calls;
      }
    }
  );
});

[alycda]

(It should be documented that the effect is reset before each test.)

How did you figure this out? I now know why my test set-up wasn't working as expected

[flotwig]

It's documented here: https://docs.cypress.io/api/commands/intercept.html#Usage

[flotwig]

How long is the lifetime of an intercept() command? (It should be documented that the effect is reset before each test.)

After each test - https://docs.cypress.io/api/commands/intercept.html#Usage

What happens when you execute multiple intercept() commands? Does the second one replace the first? Or are they "stacked" on each other?

See discussion on this issue: #9302

Is it possible to manually remove the effect of all intercept() commands within a test (or the effect of the last one if they are "stacked")?

Not currently, but this is something that would be good to add in the future for advanced use cases.

[jeremydorne]

Is there a good approach to reducing the time between an intercept getting destroyed and a new intercept getting created?

If an entire mock service is setup through intercept, there are a fair amount of instances where an application can make requests to the mocked service between when a given test clears its intercepts and the next test creates its intercepts. I've seen the guidance describe here to wait for intercepts to register but I'm not sure how to apply that logic at scale.

The issue I'm seeing roughly looks like:

describe("this suite relies on a mock service", () => {
    beforeEach(() => {
        // setup intercept service
    });

    it("tests something", () => {
        // perform some actions
    });

    // request to intercept service fails

    it("tests something else", () => {
        // perform some actions
    });
}

[the0neWhoKnocks]

Came to dig through the discussions because I too was confused about the lifecycle of intercept. Mainly I just wanted to intercept, mock response once, and destroy the intercept so all other requests behave as normal. Perhaps a chained or new method could solve this common scenario

intercept.once()
// or
interceptOnce()

[flotwig]

Like this? #8531

[the0neWhoKnocks]

Yarp, but since route is deprecated, it looks like this link is more appropriate #14513