How Playwright's Authenticated State Saves Hours of Regression Runtime

Introduction

In the fast-paced world of test automation, saving time is gold. And when it comes to regression testing, where we often run hundreds, if not thousands, of tests, time is of the essence. That's where Playwright's authenticated state can be a game-changing feature that can shave hours off your regression test runtime. By skipping the repetitive login process, your tests can focus on what truly matters.

In this post, we'll dive into how Playwright's authenticated state works, how to implement it, and its benefits to your testing process.

How Does Authenticated State Work?

At its core, Playwright's authenticated state allows you to bypass repetitive login steps in your tests. It captures the state of a logged-in session and reuses it across your tests. Instead of re-authenticating in each test scenario, you can load the session state directly, saving time and making your tests more efficient.

When logging in during a Playwright session, the tool can store this state in a file, including cookies and local storage. You load this file for subsequent tests, and then you're authenticated and ready to go. This feature is handy for large test suites, where login actions can add up in time and complexity.

Check out Playwright's authentication documentation for a more detailed look at how this works - https://playwright.dev/docs/auth.

Benefits of Using Authenticated State

Now that we understand the authenticated state let's explore how it can benefit your testing efforts.

1. Speed Boost for Your Tests

Using Playwright's authenticated state can save significant time in regression runs by eliminating the need for repeated login actions in each test case. If your regression suite contains hundreds of tests, you could run login steps hundreds of times.

Imagine this: Your test suite has 500 test cases. Each login step takes 3-5 seconds. Multiply that by 500, and you're looking at 25+ minutes of pure login time alone! By skipping the redundant logins, your test suite can run faster, giving you quicker feedback on the core functionalities that matter.

2. DRY Principle in Action

We aim to follow the DRY (Don't Repeat Yourself) throughout our automation testing. Instead of duplicating the login logic in every test, you perform the login process once, save the state, and reuse it across multiple tests.

This reduces test maintenance because you only need to update your login code in one place, making your test cases cleaner and easier to understand. Each test can focus on a single responsibility, verifying a specific feature or interaction, without worrying about authentication.

3. Fail Fast

The "fail fast" principle is valuable in this scenario. If the login process fails during the state capture, it prevents time from being wasted running tests that would inevitably fail due to authentication issues.

Drawbacks to Watch Out For

Of course, no technique is perfect. Here are some potential drawbacks when using an authenticated state in your tests.

1. State Sensitivity in Tests

You must be cautious if your test journey involves logging out, updating user profiles, or interacting with data affecting session tokens. These actions could modify the state you've captured, leading to unexpected test failures when the same state is used across multiple tests. For example, if one test logs the user out but another test expects the user to remain logged in, you'll encounter problems.

To avoid this, you need to be selective about which test cases you run with a stored state. Personally, I maintain this at a file level.

2. State Expiry

Sometimes, session tokens expire, or the application logic changes in a way that invalidates previously saved authenticated states. When this happens, tests may fail in confusing ways. To mitigate this, you should refresh the state periodically or ensure your test environments are set up to maintain valid sessions.

Mindset Shift: Test Isolation and Single Responsibility

Testers must embrace test isolation to benefit fully from Playwright's authenticated state. Each test should handle only one responsibility and avoid affecting the state of other tests. This aligns with the single responsibility principle in automation, where each test case should verify one thing and do it well.

Using authenticated state complements this model, allowing tests to focus on specific functionality without worrying about authentication. It also pairs well with the Page Object Model (POM), which encourages modular, reusable components for interacting with your application's UI. Once logged in, your page objects can go straight to the endpoints they need to test, streamlining your workflow further.

Conclusion

Leveraging Playwright's authenticated state can dramatically speed up your regression tests, keeping your test cases focused and efficient. Adopting this feature reduces repetitive login steps, fails faster when issues arise, and ensures your test suite remains DRY and maintainable. However, as with any tool, careful planning is necessary to avoid the pitfalls of a shared state.

Ready to streamline your tests? Give Playwright's authenticated state a try and watch your regression times shrink.