Understanding Flaky Test Failures, Network Stubbing Issues, and Test Performance Bottlenecks in Cypress

Cypress provides fast and reliable testing, but unstable tests, unreliable network stubbing, and slow test execution can reduce its effectiveness.

Common Causes of Cypress Issues

• Flaky Test Failures: Improper test synchronization, dependency on external APIs, and race conditions in UI interactions.
• Network Stubbing Issues: Incorrect request interception, improper response handling, and conflicts with backend APIs.
• Test Performance Bottlenecks: Long-running test suites, excessive DOM interactions, and inefficient fixture loading.
• Scalability Constraints: Lack of parallelization, excessive test retries, and browser resource limitations.

Diagnosing Cypress Issues

Debugging Flaky Test Failures

Check test retries for failure patterns:

npx cypress run --retries 3

Ensure proper test synchronization:

cy.get("#element").should("be.visible");

Analyze test failure screenshots and videos:

cypress/screenshots/

Identifying Network Stubbing Issues

Verify intercepted network requests:

cy.intercept("GET", "/api/data").as("getData");
cy.wait("@getData");

Check API response delays:

cy.wait(2000); // Avoid unnecessary static waits

Ensure backend requests match test stubs:

cy.intercept("POST", "/api/login", { statusCode: 200, body: { token: "abc123" } });

Detecting Test Performance Bottlenecks

Measure test execution time:

npx cypress run --config video=false

Optimize test commands:

cy.get("#submit").click();

Reduce fixture loading overhead:

cy.fixture("user.json").then((user) => {
    cy.get("#name").type(user.name);
});

Profiling Scalability Constraints

Enable parallel test execution:

npx cypress run --record --parallel

Optimize browser resource utilization:

npx cypress run --browser chrome

Fixing Cypress Issues

Fixing Flaky Test Failures

Use proper assertions:

cy.get("#element").should("exist").and("be.visible");

Ensure correct test isolation:

beforeEach(() => {
    cy.visit("/login");
});

Fixing Network Stubbing Issues

Mock API responses correctly:

cy.intercept("GET", "/api/data", { fixture: "data.json" });

Ensure correct request matching:

cy.intercept("POST", "/api/submit", req => {
    req.reply({ statusCode: 201, body: { success: true } });
});

Fixing Test Performance Bottlenecks

Reduce unnecessary page reloads:

Cypress.Cookies.preserveOnce("session_id");

Optimize test execution order:

npx cypress run --config testFiles="fast-tests/*"

Improving Scalability

Use test sharding:

npx cypress run --group smoke-tests

Reduce redundant tests:

it.only("focus on specific test", () => { });

Preventing Future Cypress Issues

• Implement proper synchronization techniques to avoid flaky tests.
• Use network stubbing consistently to prevent external API dependencies.
• Optimize test execution time by minimizing unnecessary browser interactions.
• Enable parallel test execution to scale Cypress test runs efficiently.

Conclusion

Cypress issues arise from unstable test executions, improper network stubbing, and slow test performance. By refining test strategies, enforcing proper synchronization, and leveraging parallel execution, developers can improve test reliability and efficiency.

FAQs

1. Why are my Cypress tests failing inconsistently?

Flaky tests occur due to race conditions, missing assertions, or dependency on unstable external APIs.

2. How do I properly stub network requests in Cypress?

Use cy.intercept() with correct request matching and response handling to ensure stable network stubbing.

3. Why are my Cypress tests running slow?

Long test execution times can be caused by excessive DOM interactions, unnecessary fixture loading, and redundant browser refreshes.

4. How can I speed up my Cypress test runs?

Enable parallel execution, optimize test commands, and reduce fixture loading overhead.

5. How do I debug failing Cypress tests?

Analyze failure screenshots, use cy.log() for debugging, and enable detailed test execution logs.