Best practices for selectors in Cypress - Build an Automation Script

Verify login form elements using best practice selectors

Preconditions (1)

Step 1: Locate the email input field using a data-cy attribute and type '[e-mail]'

Step 2: Locate the password input field using a data-cy attribute and type 'Password123!'

Step 3: Locate the login button using a data-cy attribute and click it

Step 4: Verify that the URL changes to '/dashboard' after login

✅ Expected Result: The login form fields are located using best practice selectors, login is successful, and user is redirected to the dashboard page

Automation Requirements - Cypress

Assertions Needed:

Verify email input field is found and accepts input

Verify password input field is found and accepts input

Verify login button is found and clickable

Verify URL changes to '/dashboard' after clicking login

Best Practices:

Use data-cy attributes for selectors instead of classes or IDs

Avoid using brittle selectors like XPath or overly complex CSS selectors

Use explicit assertions to confirm element visibility and interaction

Use Cypress commands consistently (cy.get, cy.type, cy.click, cy.url)

Automated Solution

Cypress

describe('Login form test with best practice selectors', () => {
  beforeEach(() => {
    cy.visit('/login');
  });

  it('should login successfully using data-cy selectors', () => {
    cy.get('[data-cy=email-input]')
      .should('be.visible')
      .type('[e-mail]');

    cy.get('[data-cy=password-input]')
      .should('be.visible')
      .type('Password123!');

    cy.get('[data-cy=login-button]')
      .should('be.visible')
      .click();

    cy.url().should('include', '/dashboard');
  });
});

This test uses data-cy attributes as selectors, which are stable and not affected by styling or layout changes.

Each element is first checked to be visible before interacting, ensuring the test waits for the element properly.

The test types into the email and password fields, then clicks the login button.

Finally, it asserts that the URL includes '/dashboard' to confirm successful login.

This approach avoids brittle selectors like classes or XPath and uses Cypress commands consistently for clarity and maintainability.

Common Mistakes - 4 Pitfalls

Using CSS classes or IDs that may change frequently as selectors

Using XPath selectors in Cypress tests

{'mistake': 'Not asserting element visibility before interaction', 'why_bad': 'Trying to interact with elements not visible or not yet loaded can cause flaky tests.', 'correct_approach': "Use assertions like .should('be.visible') before typing or clicking."}

{'mistake': 'Hardcoding full URLs in assertions', 'why_bad': 'Full URLs may change between environments, causing tests to fail unnecessarily.', 'correct_approach': "Assert on URL parts using .should('include', '/dashboard') to allow flexibility."}

Bonus Challenge

Now add data-driven testing with 3 different sets of valid login credentials

Show Hint

Practice

1. Which of the following is the best practice for choosing selectors in Cypress tests?

easy

A. Use text content that may change frequently.

B. Use CSS classes that might change with styling updates.

C. Use element positions like :nth-child() selectors.

D. Use unique IDs or custom data attributes for selectors.

Solution

1. Step 1: Understand selector stability

   Selectors should be stable and unique to avoid breaking tests when UI changes.

2. Step 2: Evaluate options for stability

   IDs and custom data attributes are stable and unique, unlike classes or text that can change.

3. Final Answer:

   Use unique IDs or custom data attributes for selectors. -> Option D

4. Quick Check:

   Stable selectors = IDs or data attributes [OK]

Hint: Pick selectors that rarely change, like IDs or data attributes [OK]

Common Mistakes:

• Using CSS classes that change with styling
• Selecting by visible text that may vary
• Relying on element order which can shift

2. Which of the following is the correct syntax to select an element with a custom attribute data-test='submit-btn' in Cypress?

easy

A. cy.get('[data-test=submit-btn]')

B. cy.get('data-test=submit-btn')

C. cy.get('#submit-btn')

D. cy.get('.submit-btn')

Solution

1. Step 1: Recall attribute selector syntax

   In CSS selectors, attributes are selected with square brackets and quotes if needed.

2. Step 2: Match correct Cypress syntax

   cy.get('[data-test=submit-btn]') correctly uses attribute selector syntax.

3. Final Answer:

   cy.get('[data-test=submit-btn]') -> Option A

4. Quick Check:

   Attribute selectors use brackets [] [OK]

Hint: Use brackets [] around attribute selectors in cy.get() [OK]

Common Mistakes:

• Omitting brackets for attribute selectors
• Using ID or class selectors incorrectly
• Missing quotes around attribute values

3. Given the HTML snippet:

<button data-cy='login-btn' class='btn primary'>Login</button>

What will cy.get('.btn.primary').click() do if the class changes to btn secondary later?

medium

A. The test will fail because the selector no longer matches.

B. The test will still pass because class selectors are stable.

C. The test will click a different button automatically.

D. The test will ignore the class and find the button by text.

Solution

1. Step 1: Understand selector dependency on class names

   The selector '.btn.primary' depends on the button having both classes 'btn' and 'primary'.

2. Step 2: Analyze effect of class change

   If the class changes to 'btn secondary', the selector '.btn.primary' no longer matches, causing failure.

3. Final Answer:

   The test will fail because the selector no longer matches. -> Option A

4. Quick Check:

   Class selectors break if classes change [OK]

Hint: Avoid class selectors that can change with styling [OK]

Common Mistakes:

• Assuming class selectors are stable
• Expecting automatic fallback to other selectors
• Thinking text selectors are used automatically

4. You wrote this Cypress selector: cy.get('button.submit-btn') but the test fails because the button has no class submit-btn. How can you fix it following best practices?

medium

A. Add the class submit-btn to the button in HTML.

B. Change selector to use a stable attribute like data-cy='submit-btn'.

C. Use cy.get('button') to select all buttons.

D. Use cy.contains('Submit') to select by text.

Solution

1. Step 1: Identify the problem with class selector

   The button lacks the class 'submit-btn', so the selector fails.

2. Step 2: Apply best practice for stable selectors

   Using a custom attribute like data-cy='submit-btn' is stable and recommended.

3. Final Answer:

   Change selector to use a stable attribute like data-cy='submit-btn'. -> Option B

4. Quick Check:

   Stable selectors use custom attributes [OK]

Hint: Use custom data attributes for stable selectors [OK]

Common Mistakes:

• Relying on missing or changing classes
• Selecting too broadly causing flaky tests
• Using text selectors that may change

5. You want to write a Cypress test that clicks the 'Save' button inside a form. The button has no ID but has data-test='save-btn'. The form has multiple buttons with different data-test attributes. Which selector is best to ensure you click the correct button inside the form?

hard

A. cy.get('form button').eq(0).click()

B. cy.get('[data-test=save-btn]').click()

C. cy.get('form').find('[data-test=save-btn]').click()

D. cy.get('button').contains('Save').click()

Solution

1. Step 1: Understand the need for context-specific selection

   Since multiple buttons have data-test attributes, selecting within the form narrows scope.

2. Step 2: Choose selector that scopes to form and targets correct button

   Using cy.get('form').find('[data-test=save-btn]') ensures the button inside the form is selected.

3. Final Answer:

   cy.get('form').find('[data-test=save-btn]').click() -> Option C

4. Quick Check:

   Scoped selectors avoid ambiguity [OK]

Hint: Scope selectors inside containers to avoid ambiguity [OK]

Common Mistakes:

• Selecting buttons globally causing wrong clicks
• Using text selectors that may match multiple elements
• Using index-based selectors that can break easily