Engineering is accelerating.End-to-end testing is falling behind.

“The most critical skill to have in your toolbox is a high quality verification skill.”

From The Complete Guide to pstack Pt. 1 · Aug 31, 2026

1. 2.1

   Real browsers are the most realistic test.

   Exercising your web application through a real browser is as close as you can get to what your users experience. That makes it the most valuable kind of testing.

2. 2.2

   Code is the best way to drive a browser.

   It is the cheapest, most predictable and most scalable way to exercise a web application.

3. 2.3

   The ecosystem has done the hard work.

   Controlling web applications through code comes with real engineering problems. Tools like Playwright already solve many of them.

1. 3.1

   Agents are phenomenally good at writing code.

   That makes them phenomenally good at exercising web applications, by writing code.

2. 3.2

   Agents shouldn't reinvent the wheel.

   When agents use existing tooling, they inherit the problems it already solves: dynamic setup and teardown of data, fixtures, reusable helpers.

3. 3.3

   One suite, one shared understanding.

   When you and your agents exercise your application through the same code, you work from a shared understanding of it, and improve it together.

4. 3.4

   A good suite makes everyone better.

   Maintaining a good end-to-end test suite meaningfully improves how both you and your agents work.

5. 3.5

   The best context is outside the execution loop.

   An agent driving your tests has a narrow view of your application state. An agent that writes and maintains your tests can draw on context from pull requests and suite history to make better decisions.

1. 4.1

   There is no silver bullet for verification.

   Building a great test suite is a process, not an overnight job.

2. 4.2

   Work with real infrastructure.

   End-to-end tests expose your application for what it is. They force you to deal with slow, unreliable infrastructure and race conditions.

3. 4.3

   Work with real errors.

   End-to-end tests surface the errors your users actually encounter, not the pretty picture unit and integration tests paint.

4. 4.4

   They require real engineering, love and care.

   Done right, they force you to meaningfully improve your application.

Working with your end-to-end test suite should mean improving your application, not fighting your tooling.

1. 5.1

   Everyone on your team should feel comfortable working with end-to-end tests regularly.

2. 5.2

   Your investment in testing should make your team meaningfully more productive.