Slot testing in Cypress - Test Execution Trace

Test Overview

This test checks if a web page correctly displays content passed into a named slot in a web component. It verifies that the slot content is rendered and visible to the user.

Test Code - Cypress

Cypress

describe('Slot testing', () => {
  it('should display content inside the named slot', () => {
    cy.visit('/slot-test-page')
    cy.get('my-component').shadow().find('slot[name="header"]').then(slot => {
      cy.wrap(slot).invoke('prop', 'assignedNodes').should('have.length.greaterThan', 0)
    })
    cy.get('my-component').contains('Header Content').should('be.visible')
  })
})

Execution Trace - 4 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test runner initialized, no browser opened yet	—	PASS
2	Browser opens and navigates to '/slot-test-page'	Page with <my-component> loaded, slot elements present in shadow DOM	—	PASS
3	Find the named slot 'header' inside the shadow DOM of <my-component>	Slot element located inside shadow root	Check that slot has assigned nodes (content passed into slot)	PASS
4	Verify that the content 'Header Content' is visible on the page	Content inside slot is rendered and visible	Assert that 'Header Content' text is visible	PASS

Failure Scenario

Failing Condition: The named slot 'header' has no assigned content or the content is not visible

Execution Trace Quiz - 3 Questions

What does the test verify about the named slot 'header'?

A That the slot has content assigned and it is visible

B That the slot is empty

C That the slot is hidden

D That the slot is disabled

Key Result

Always verify that content passed into slots is actually rendered and visible, especially when testing web components with shadow DOM.

Practice

1. What is the main purpose of slot testing in Cypress?

easy

A. To check network requests made by the application

B. To validate CSS styles of static elements

C. To test database connections

D. To verify dynamic content inside component slots renders correctly

Solution

1. Step 1: Understand slot testing concept

   Slot testing focuses on dynamic content areas called slots inside components.

2. Step 2: Identify Cypress role in slot testing

   Cypress commands are used to find slots and verify their content correctness.

3. Final Answer:

   To verify dynamic content inside component slots renders correctly -> Option D

4. Quick Check:

   Slot testing = Verify dynamic slot content [OK]

Hint: Slots hold dynamic content; test their presence and correctness [OK]

Common Mistakes:

• Confusing slot testing with network or database testing
• Ignoring fallback content in slots
• Testing only static elements instead of slots

2. Which Cypress command correctly selects a named slot with the name 'header'?

easy

A. cy.get('#header')

B. cy.get('slot[name="header"]')

C. cy.get('div.header')

D. cy.get('slot#header')

Solution

1. Step 1: Understand slot selector syntax

   Named slots use the slot tag with a name attribute, so selector is slot[name="header"].

2. Step 2: Match Cypress command to selector

   Only cy.get('slot[name="header"]') correctly targets the named slot.

3. Final Answer:

   cy.get('slot[name="header"]') -> Option B

4. Quick Check:

   Named slot selector = slot[name="..."] [OK]

Hint: Use attribute selector for named slots: slot[name="..."] [OK]

Common Mistakes:

• Using class or id selectors instead of slot attribute
• Confusing slot tag with div or other elements
• Missing quotes around attribute value

3. Given this Cypress test snippet:

cy.get('slot[name="footer"]').should('contain.text', 'Contact us')

What will happen if the slot named 'footer' contains the text 'Contact us today'?

medium

A. Test passes because 'Contact us' is part of the slot text

B. Test fails because exact text does not match

C. Test throws a syntax error

D. Test passes only if the slot is visible

Solution

1. Step 1: Understand the assertion used

   The assertion should('contain.text', 'Contact us') checks if the slot text includes the substring 'Contact us'.

2. Step 2: Analyze the slot content

   The slot text is 'Contact us today', which contains 'Contact us' as a substring.

3. Final Answer:

   Test passes because 'Contact us' is part of the slot text -> Option A

4. Quick Check:

   contain.text checks substring presence [OK]

Hint: contain.text checks substring, not exact match [OK]

Common Mistakes:

• Assuming contain.text requires exact match
• Confusing contain.text with equals assertion
• Ignoring slot visibility requirement

4. You wrote this Cypress test:

cy.get('slot[name="main"]').should('have.text', 'Welcome')

But the test fails even though the slot shows 'Welcome to our site'. What is the likely problem?

medium

A. Cypress cannot test slot content

B. The slot selector is incorrect

C. Using 'have.text' requires exact text match, so it fails

D. The slot is not visible on the page

Solution

1. Step 1: Understand 'have.text' assertion

   'have.text' checks for exact text equality, not substring.

2. Step 2: Compare expected and actual slot text

   Expected 'Welcome' does not exactly match 'Welcome to our site', so assertion fails.

3. Final Answer:

   Using 'have.text' requires exact text match, so it fails -> Option C

4. Quick Check:

   have.text = exact match, contain.text = substring [OK]

Hint: Use contain.text for partial matches, have.text for exact [OK]

Common Mistakes:

• Confusing have.text with contain.text
• Assuming slot selector is wrong without checking
• Ignoring visibility but test fails due to text mismatch

5. You want to test a component with a default slot and a named slot 'sidebar'. The default slot shows fallback text 'No content'. Which Cypress test correctly verifies fallback and named slot content?

hard

A. cy.get('slot:not([name])').should('contain.text', 'No content'); cy.get('slot[name="sidebar"]').should('contain.text', 'Menu')

B. cy.get('slot[name="default"]').should('contain.text', 'No content'); cy.get('slot#sidebar').should('contain.text', 'Menu')

C. cy.get('slot').should('contain.text', 'No content'); cy.get('slot[name="sidebar"]').should('contain.text', 'Menu')

D. cy.get('slot.default').should('contain.text', 'No content'); cy.get('slot.sidebar').should('contain.text', 'Menu')

Solution

1. Step 1: Select default slot correctly

   The default slot has no name attribute, so selector is slot:not([name]).

2. Step 2: Select named slot 'sidebar'

   Named slot selector is slot[name="sidebar"].

3. Step 3: Verify fallback and named slot content

   Use contain.text to check fallback 'No content' and sidebar 'Menu'.

4. Final Answer:

   cy.get('slot:not([name])').should('contain.text', 'No content'); cy.get('slot[name="sidebar"]').should('contain.text', 'Menu') -> Option A

5. Quick Check:

   Default slot = slot:not([name]), named slot = slot[name="..."] [OK]

Hint: Default slot has no name attribute; use :not([name]) selector [OK]

Common Mistakes:

• Using slot[name="default"] which does not exist
• Using class or id selectors on slot elements
• Not distinguishing default slot from named slots