Understanding Flaky Cypress Tests

Flaky tests in Cypress occur when tests pass or fail inconsistently due to timing issues, network delays, or improper state handling. Identifying and resolving these issues is essential for maintaining reliable test automation.

Root Causes

1. Dynamic Elements Not Available

Tests may fail when trying to interact with elements that are not yet available in the DOM:

// Example: Element not yet rendered
cy.get('#submit-button').click();  // Might fail if button is not visible immediately

2. Network Delays Affecting Requests

Tests relying on API responses may fail due to slow or delayed network requests:

// Example: Unreliable network request
cy.intercept('GET', '/api/data').as('getData');
cy.wait('@getData');
cy.get('.table-row').should('exist');  // Might fail if data loads slowly

3. State Pollution Between Tests

State from previous tests affecting subsequent tests can cause inconsistent behavior:

// Example: State carried over between tests
describe('Test Suite', () => {
  it('Test 1', () => {
    cy.setCookie('session', 'abc123');
  });
  it('Test 2', () => {
    cy.get('.session-required').should('exist');  // Fails if session was cleared
  });
});

4. Hardcoded Waits

Using fixed delays (cy.wait()) instead of dynamic waits can introduce flakiness:

// Example: Hardcoded wait
cy.wait(5000); // Arbitrary timeout that may fail under different conditions

5. Race Conditions

Tests may attempt to interact with elements before they are fully rendered:

// Example: Race condition
cy.get('#modal-button').click();
cy.get('#modal-content').should('be.visible');

Step-by-Step Diagnosis

To diagnose flaky Cypress tests, follow these steps:

1. Enable Debugging Logs: Run Cypress with verbose logging to identify timing issues:

# Example: Run Cypress with debugging
DEBUG=cypress:* npx cypress run

2. Use Cypress Test Retries: Enable retries to determine if a test is intermittently failing:

// Example: Enable test retries
module.exports = {
  retries: {
    runMode: 2,
    openMode: 1,
  },
};

3. Analyze Network Requests: Verify API response times and status codes:

// Example: Log API responses
cy.intercept('GET', '/api/data', (req) => {
  req.reply((res) => {
    console.log('Response Status:', res.statusCode);
  });
});

4. Check Element Visibility: Ensure Cypress waits for elements dynamically:

// Example: Wait dynamically for element to appear
cy.get('#submit-button', { timeout: 10000 }).should('be.visible');

5. Run Tests in Isolation: Use beforeEach() hooks to reset state:

// Example: Reset state before each test
beforeEach(() => {
  cy.clearCookies();
  cy.reload();
});

Solutions and Best Practices

1. Use Assertions with Timeouts

Ensure Cypress waits dynamically for elements to be available:

// Example: Dynamic waiting
cy.get('#modal', { timeout: 10000 }).should('be.visible');

2. Optimize Network Request Handling

Stub API responses to control test execution:

// Example: Mock API response
cy.intercept('GET', '/api/data', { fixture: 'mockData.json' }).as('getData');

3. Reset State Between Tests

Ensure tests do not depend on previous state:

// Example: Reset session before each test
beforeEach(() => {
  cy.clearCookies();
  cy.clearLocalStorage();
});

4. Avoid Hardcoded Waits

Use assertions instead of arbitrary delays:

// Example: Replace hardcoded waits
cy.get('.loader').should('not.exist');

5. Resolve Race Conditions

Use should() assertions to wait for elements:

// Example: Wait for modal before interacting
cy.get('#modal-button').click();
cy.get('#modal-content').should('be.visible');

Conclusion

Flaky Cypress tests can undermine test automation reliability. By using dynamic waits, handling network requests effectively, resetting state between tests, and avoiding race conditions, developers can achieve stable and predictable test execution. Regular debugging and best practices help improve test consistency and maintainability.

FAQs

• What causes flaky tests in Cypress? Flaky tests are usually caused by dynamic elements, network delays, race conditions, or reliance on previous test state.
• How can I debug flaky Cypress tests? Use logging, network request stubs, test retries, and verbose debugging options.
• What is the best way to wait for elements in Cypress? Use assertions like should() with timeouts instead of hardcoded cy.wait() delays.
• How can I make my Cypress tests more reliable? Reset state between tests, use dynamic waits, and stub API responses to ensure predictable results.
• How do I handle slow API responses in Cypress? Use cy.intercept() to mock API responses and prevent test failures due to network latency.