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What is End-to-End (E2E) Testing?
End-to-end (E2E) testing is an approach to quality assurance (QA) that assesses how well a software application works from the end user’s point of view. E2E tests simulate real-world user scenarios to verify that the entire application flow, including interactions with external systems, databases, and APIs, works together seamlessly and delivers the intended functionality.
While this type of system testing does assess an application’s technical interactions, E2E is considered to be a functional test because its primary goal is to validate the user journey across all integrated systems and workflows.
Key Takeaways
- End-to-end testing is used to validate the user journey from start to finish.
- E2E tests simulate real-world use cases to assess the entire application flow, including interactions with external components.
- Each End-to-End test case has a clear objective and an expected outcome.
- Manual E2E tests are useful for exploratory testing at the beginning of a software development project.
- Agile software development teams often include automated E2E tests in their CI/CD pipelines to validate the user journey after each code commit.
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How E2E Testing Works
E2E tests can be conducted manually or automatically.
- Manual testing requires a software tester to complete common tasks, verify expected outcomes, and flag unexpected outcomes.
- Automated tests use a testing framework and scripts to simulate user interactions programmatically.
The choice between manual and automated E2E testing often depends on factors like the software project’s stage, complexity, budget, and available resources.
For example, manual E2E tests could be used as smoke tests for smaller development projects.
End-to-End (E2E) Tests in 10 Easy Steps
- Gather stakeholders to understand the common paths that users take.
- Identify which paths are most important to end users and the business.
- Document the purpose of each E2E test, the steps involved, and the expected outcomes.
- Select a testing tool that fits the surrounding technology stack.
- Set up a test environment that mirrors the production environment as closely as possible.
- Write test scenarios for the user flows identified in Step 2.
- Execute the tests. This can be done manually in a local testing environment or automatically in the cloud within a CI/CD pipeline.
- Monitor the results to ensure the application behaves as expected.
- If a test fails, investigate the cause and fix it.
- Refine the tests to handle edge cases or unexpected behaviors as needed.
When to Run E2E Tests
End-to-end tests are typically run before the code is moved to a staging environment.
Scenarios when it’s useful to run E2E tests include:
- Before major releases.
- After significant code changes.
- After bug fixes.
- During regression testing.
- After server upgrades, database migrations, or changes in third-party services.
- During automated nightly builds for CI/CD pipelines.
Project management software tools can be used to track test results to ensure transparency and accountability for use cases with regulatory compliance requirements.
End-to-End Testing Lifecycle
The end-to-end testing lifecycle follows a structured approach that is similar to other software testing processes, but the focus is on testing the entire application workflow.
As an application evolves with new features, user interface (UI) changes, or modifications in workflows, E2E tests need to be updated to reflect these changes. This can be particularly time-consuming because E2E tests often cover broad user flows that can be affected by even small changes in the application.
Types of End-to-End Testing
End-to-end tests can be categorized based on their scope and focus. Typically, QA teams combine different types of E2E testing to ensure comprehensive coverage for a wide variety of use cases.
End-to-End Testing Tools
Testing frameworks like Playwright provide tools and libraries to simplify test script development and execution.
Essentially, they will automatically simulate user actions like clicking buttons or filling out forms and then verify responses that meet tester-defined expectations.
Metrics to Use in End-to-End Testing
Key metrics that are commonly used in E2E testing include:
End-to-End Testing vs. Other Software Testing
DevOps teams can use E2E testing along with unit tests, integration tests, and other QA tests, to validate an application works in real-world usage scenarios.
Types of Functional QA Tests
Focus: Validate individual components or functions in isolation
When to perform: During development
Test maintenance requirements: Low
Example: Test a function that allows the user to choose a payment option
Focus: Validate interactions between integrated components or modules
When to perform: After unit testing
Test maintenance requirements: Moderate
Example: Test the data flow between an input form and a database
Focus: Validate user workflows
When to perform: After integration testing
Test maintenance requirements: High
Example: Test a user’s ability to log in, browse products, and complete a purchase
Focus: Validate business requirements have been met
When to perform: Before release
Test maintenance requirements: Moderate
Example: Assess whether the software meets defined business requirements
Focus: Ensure code changes do not break existing functionality
When to perform: After any change to the codebase
Test maintenance requirements: High
Example: Test login functionality after a security update to ensure it still works
End-to-End Testing Best Practices
Here are some best practices for end-to-end testing:
- Automate tests whenever possible
- Integrate E2E tests into CI/CD pipelines whenever possible
- Help ensure tests are maintainable by avoiding overly complex end user scenarios
- Regularly review and update tests to reflect changes in the application
- Use test results to address issues as quickly as possible
End-to-End Test Pros and Cons
As with any type of quality assurance test, E2E tests have both advantages and disadvantages.
- Simulates real-world scenarios from the user’s point of view
- Validates the entire user flow, including external dependencies
- Reduces the risk of critical failures in production
- Can take a long time to run and require significant computational resources
- Can be brittle and require frequent updates
- Debugging can be challenging
The Bottom Line
There can be a lot of overlap between definitions for end-to-end testing and systems testing because both types of tests are used to validate the entire application as a whole, rather than focusing on individual components or units of code.
You could say that E2E testing is just a type of functional system testing that focuses on how the application behaves from the user’s point of view. You could also argue that systems testing is just a broader type of E2E testing that includes non-functional requirements like performance, security, and reliability.
