Cypress: Experimental Fast Visibility Configuration

Hey guys! Today, we're diving deep into a cool new feature request for Cypress that could seriously speed up your tests. It's all about visibility checks, and how to make them, well, faster. Let's break it down.

What's the Big Idea?

The core proposal is to introduce a new configuration option called experimentalFastVisibility. Imagine having a switch that you can flip to enable a more optimized approach to determining element visibility in your Cypress tests. This isn't just a global on/off thing; the beauty lies in its flexibility. You could enable it for specific test suites, individual tests, or even within your setup and teardown hooks. Think of the possibilities!

Acceptance Criteria: Making It Real

To make this experimentalFastVisibility option a reality, we need a few things in place. These acceptance criteria ensure that the feature is not only implemented but also works as expected:

1. Configuration Root: The option should be available right at the top level of your Cypress configuration file (cypress.config.js or cypress.config.ts). This makes it easy to find and set up.

2. Granular Control: You should be able to toggle this feature on or off within describe, context, and it blocks. This means you can apply it to specific test suites or individual test cases.

3. Hook Integration: The option needs to be controllable within before and after hooks. This allows you to enable or disable the fast visibility checks for setup and teardown routines.

4. Under the Hood: When enabled, the following should use the optimized approach:

   • jQuery's :visible and :hidden selectors.
   • Actionability checks (i.e., when Cypress determines if an element is ready to be interacted with).
   • Visible/Hidden assertions (e.g., .should('be.visible')).

Why Do We Need This?

You might be wondering, "Why bother?" Well, the current visibility checks in Cypress can be a bit… thorough. They make sure, really sure, that an element is visible before interacting with it. This involves checking a variety of factors, such as whether the element has display: none, visibility: hidden, if it has zero width or height, if it's clipped by an ancestor, and so on. All these checks add up, and while they ensure accuracy, they can also slow down your tests.

The "fast" algorithm, on the other hand, aims to be quicker by potentially skipping some of these checks. However, this speed comes with a trade-off. The fast algorithm might have some functional differences in its semantics. In other words, it might not always agree with the current, more rigorous approach. That's why having the ability to enable or disable it on a case-by-case basis is crucial. It allows you to use the faster approach where appropriate, without sacrificing accuracy in more critical areas of your application.

Diving Deeper: Use Cases and Examples

Let's explore some specific scenarios where this experimentalFastVisibility option could be a game-changer.

Scenario 1: Speeding Up Large Test Suites

Imagine you have a massive test suite with hundreds or even thousands of tests. Many of these tests might involve simple visibility checks that don't require the full rigor of the current algorithm. By enabling experimentalFastVisibility for the entire suite, you could potentially shave off a significant amount of time, reducing your overall test execution time.

// cypress.config.js
module.exports = {
  experimentalFastVisibility: true,
  e2e: {
    setupNodeEvents(on, config) {
      // implement node event listeners here
    },
  },
};

Scenario 2: Targeting Specific Slow Tests

Perhaps you've identified a few specific tests that are particularly slow due to visibility checks. Instead of applying the faster approach globally, you can target those individual tests.

// Example: cypress/e2e/my_test.cy.js
describe('My Slow Test Suite', () => {
  it('My slow visibility test', { experimentalFastVisibility: true }, () => {
    cy.get('#myElement').should('be.visible'); // Uses the faster algorithm
  });

  it('Another test in the same suite', () => {
    cy.get('#anotherElement').should('be.visible'); // Uses the default algorithm
  });
});

Scenario 3: Conditional Visibility Checks

In some cases, you might want to use the faster algorithm only under certain conditions. For example, you might enable it only when running tests in a CI environment, where speed is more critical than absolute accuracy.

// cypress.config.js
module.exports = {
  experimentalFastVisibility: process.env.CI === 'true',
  e2e: {
    setupNodeEvents(on, config) {
      // implement node event listeners here
    },
  },
};

Scenario 4: Before and After Hooks

Using experimentalFastVisibility inside before and after hooks can be useful for setting up specific conditions for your tests. For instance, you might want to ensure that certain elements are quickly made visible before a test runs.

// Example: cypress/e2e/my_test.cy.js

describe('Test Suite with Hooks', () => {
  beforeEach(() => {
    Cypress.config('experimentalFastVisibility', true);
    // Quickly make an element visible before each test
    cy.get('#myElement').invoke('show');
  });

  afterEach(() => {
    Cypress.config('experimentalFastVisibility', false);
    // Reset the visibility setting after each test
  });

  it('My test', () => {
    cy.get('#myElement').should('be.visible'); // Uses the faster algorithm
  });
});

Potential Challenges and Considerations

While the experimentalFastVisibility option sounds amazing, there are a few potential challenges and considerations to keep in mind:

• Inconsistencies: As mentioned earlier, the faster algorithm might not always agree with the current algorithm. This could lead to inconsistencies in your tests, where a test passes with the faster algorithm but fails with the default algorithm, or vice versa.
• Debugging: If you encounter unexpected behavior, it might be difficult to determine whether it's due to the faster algorithm or some other issue in your code. You'll need to carefully investigate and compare the behavior with and without the experimentalFastVisibility option enabled.
• Maintenance: As the Cypress team continues to improve and refine the visibility checks, the differences between the faster algorithm and the default algorithm might change over time. This could require you to revisit your tests and adjust your usage of the experimentalFastVisibility option accordingly.

The Bottom Line

The experimentalFastVisibility configuration option has the potential to significantly speed up your Cypress tests, especially in large test suites or in scenarios where you need to quickly check the visibility of elements. However, it's important to use it judiciously and be aware of the potential trade-offs. By enabling it on a case-by-case basis and carefully monitoring your tests, you can leverage the benefits of the faster algorithm without sacrificing accuracy or reliability.

This feature could be a real game-changer for Cypress testing, offering a flexible way to optimize test execution speed. Keep an eye out for updates and give it a try when it becomes available! Happy testing, everyone!