Shadow DOM access in Cypress - Test Execution Trace

Test Overview

This test opens a webpage containing a shadow DOM element. It accesses a button inside the shadow DOM and clicks it. Then it verifies that clicking the button changes the text inside the shadow DOM as expected.

Test Code - Cypress

Cypress

describe('Shadow DOM access test', () => {
  it('should click button inside shadow DOM and verify text change', () => {
    cy.visit('https://example.com/shadowdom')
    cy.get('my-shadow-host').shadow().find('button#shadow-btn').click()
    cy.get('my-shadow-host').shadow().find('span#status').should('have.text', 'Clicked!')
  })
})

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test runner initialized, no browser opened yet	—	PASS
2	Browser opens and navigates to 'https://example.com/shadowdom'	Browser shows the page with a custom element 'my-shadow-host' containing shadow DOM	—	PASS
3	Find 'my-shadow-host' element and access its shadow DOM	'my-shadow-host' element is found, shadow DOM is accessible	—	PASS
4	Find button with id 'shadow-btn' inside shadow DOM and click it	Button inside shadow DOM is found and clicked	—	PASS
5	Find span with id 'status' inside shadow DOM and check its text	Span inside shadow DOM is found	Verify span text is 'Clicked!'	PASS
6	Test ends	Test completed successfully	—	PASS

Failure Scenario

Failing Condition: The button inside the shadow DOM is not found or not clickable

Execution Trace Quiz - 3 Questions

Which Cypress command is used to access elements inside the shadow DOM?

A .shadow()

B .findShadow()

C .shadowRoot()

D .getShadow()

Key Result

When testing elements inside shadow DOM, use the '.shadow()' command in Cypress to access the shadow root before finding elements. This ensures reliable interaction with shadow DOM elements.

Practice

1. What is the correct way to access an element inside a Shadow DOM using Cypress?

easy

A. Use cy.get('selector').shadow().find('inner-selector')

B. Use cy.get('selector').find('inner-selector') directly

C. Use cy.shadow('selector').get('inner-selector')

D. Use cy.getShadow('selector').find('inner-selector')

Solution

1. Step 1: Understand Shadow DOM access in Cypress

   Cypress requires the shadow() command to enter the Shadow DOM context before finding elements inside it.

2. Step 2: Use the correct chaining method

   The correct syntax is cy.get('selector').shadow().find('inner-selector') to access elements inside Shadow DOM.

3. Final Answer:

   Use cy.get('selector').shadow().find('inner-selector') -> Option A

4. Quick Check:

   Shadow DOM access = cy.get().shadow().find() [OK]

Hint: Always use .shadow() before .find() for Shadow DOM elements [OK]

Common Mistakes:

• Trying to find elements inside Shadow DOM without .shadow()
• Using non-existent commands like cy.shadow() or cy.getShadow()
• Assuming .find() works directly on Shadow DOM host

2. Which of the following Cypress commands correctly accesses a button with id submitBtn inside a Shadow DOM hosted by my-component?

easy

A. cy.get('my-component').find('#submitBtn')

B. cy.get('my-component').shadow().find('#submitBtn')

C. cy.shadow('my-component').get('#submitBtn')

D. cy.getShadow('my-component').find('#submitBtn')

Solution

1. Step 1: Identify the Shadow DOM host

   The element my-component is the Shadow DOM host, so we start with cy.get('my-component').

2. Step 2: Access the Shadow DOM and find the button

   We must use .shadow() to enter the Shadow DOM, then .find('#submitBtn') to locate the button inside.

3. Final Answer:

   cy.get('my-component').shadow().find('#submitBtn') -> Option B

4. Quick Check:

   Shadow DOM host + .shadow() + .find() = cy.get('my-component').shadow().find('#submitBtn') [OK]

Hint: Use .shadow() after host selector before .find() [OK]

Common Mistakes:

• Skipping .shadow() and using .find() directly
• Using non-existent commands like cy.shadow()
• Confusing host selector with inner element selector

3. Given the following Cypress code, what will be the result of the assertion?

cy.get('custom-element').shadow().find('.title').should('have.text', 'Welcome')

medium

A. The test throws a syntax error due to incorrect chaining.

B. The test fails because .shadow() cannot be chained after .get().

C. The test passes if the element with class 'title' inside the Shadow DOM has text 'Welcome'.

D. The test passes if any element with class 'title' on the page has text 'Welcome'.

Solution

1. Step 1: Understand the command chain

   The code correctly gets the Shadow DOM host custom-element, enters its Shadow DOM with .shadow(), then finds the element with class title.

2. Step 2: Evaluate the assertion

   The assertion checks if the found element's text is exactly 'Welcome'. If true, the test passes; otherwise, it fails.

3. Final Answer:

   The test passes if the element with class 'title' inside the Shadow DOM has text 'Welcome'. -> Option C

4. Quick Check:

   Correct chaining + assertion = The test passes if the element with class 'title' inside the Shadow DOM has text 'Welcome'. [OK]

Hint: Correct .shadow() chaining accesses Shadow DOM elements properly [OK]

Common Mistakes:

• Assuming .shadow() is invalid after .get()
• Confusing global elements with Shadow DOM elements
• Misunderstanding assertion target scope

4. You wrote this Cypress test but it fails to find the button inside Shadow DOM:

cy.get('widget-component').find('button.submit').click()

What is the most likely reason?

medium

A. You forgot to use .shadow() before .find() to access Shadow DOM.

B. The selector 'widget-component' is incorrect.

C. The button does not have class 'submit'.

D. Cypress cannot click buttons inside Shadow DOM.

Solution

1. Step 1: Analyze the command chain

   The code tries to find a button inside widget-component without entering Shadow DOM.

2. Step 2: Identify missing Shadow DOM access

   To access elements inside Shadow DOM, .shadow() must be used before .find(). Missing it causes failure to locate the button.

3. Final Answer:

   You forgot to use .shadow() before .find() to access Shadow DOM. -> Option A

4. Quick Check:

   Missing .shadow() causes element not found [OK]

Hint: Always insert .shadow() before .find() for Shadow DOM elements [OK]

Common Mistakes:

• Skipping .shadow() when accessing Shadow DOM
• Assuming .find() works globally inside Shadow DOM host
• Blaming selector syntax without checking Shadow DOM usage

5. You want to test a nested Shadow DOM structure where outer-component hosts a Shadow DOM containing inner-component, which itself hosts another Shadow DOM with a button #confirm. Which Cypress command chain correctly clicks the button?

hard

A. cy.get('outer-component').shadow().shadow().find('inner-component').find('#confirm').click()

B. cy.get('outer-component').find('inner-component').shadow().find('#confirm').click()

C. cy.get('outer-component').shadow().find('inner-component').find('#confirm').click()

D. cy.get('outer-component').shadow().find('inner-component').shadow().find('#confirm').click()

Solution

1. Step 1: Access the first Shadow DOM

   Start with cy.get('outer-component') and enter its Shadow DOM using .shadow().

2. Step 2: Access the nested Shadow DOM

   Find inner-component inside the first Shadow DOM, then enter its Shadow DOM again with .shadow().

3. Step 3: Find and click the button

   Inside the nested Shadow DOM, find the button with id #confirm and perform .click().

4. Final Answer:

   cy.get('outer-component').shadow().find('inner-component').shadow().find('#confirm').click() -> Option D

5. Quick Check:

   Nested Shadow DOM requires chaining .shadow() twice [OK]

Hint: Chain .shadow() for each Shadow DOM level before .find() [OK]

Common Mistakes:

• Trying to access nested Shadow DOM without multiple .shadow() calls
• Using .find() directly without entering Shadow DOM
• Confusing order of .shadow() and .find() calls