Self-healing Agents Through E2E Testing

The Agony of Being a Coding Agent’s Debug Assistant

Over the past 4 months building using Claude Code and Cursor, I tracked 103 feature implementation runs across Claude Code and Cursor. Here's what I discovered:

• 78% of implementations required at least one debugging session where I manually shuttled error logs and screenshots

• Average debugging session: 3 back-and-forth message rounds

• Only 11% of features got tests written automatically

This week's video shows how I fixed this with agent-driven E2E testing—creating autonomous feedback loops so you never have to be your agent's clipboard again.

The Real Story: Why I Chose E2E Over Unit Tests

Here's what didn't make it into the video—why E2E tests specifically solve the agent autonomy problem better than other testing approaches:

Unit Tests: Agents write them more frequently (~30% of the time in my analysis), but they miss integration issues. Your agent can write perfect logic that fails when the database connection drops or the API changes.

Integration Tests: Better coverage, but still require you to mock external services and define contracts. Agents struggle with realistic mocking—they either over-mock (missing real failures) or under-mock (flaky tests).

E2E Tests: Test the full user journey through a real browser. When they fail, it's usually something a user would actually encounter. Plus, the failure artifacts (screenshots, traces, DOM snapshots) give agents rich context that's much easier to debug than stack traces.

The trade-off? E2E tests are slower and can be flakier. But for agent-driven development, the debugging signal-to-noise ratio is dramatically better.

Why Agents Fallover In E2E Testing?

After reviewing the 103 feature implementations across Claude Code and Cursor. There are three core issues that we need to tackle:

1. Agents don’t reliably write tests.

2. The E2E tests they do write aren’t high quality.

3. They can’t self-debug failures without you ferrying logs.

🎬 Watch the Full Implementation

I walk through the complete setup process, show the actual debugging workflow in action, and demonstrate the autonomous feedback loop:

After completing the setup outlined in the video, here are my results compared against a barebone repo setup:

• 11% → 95% of my prompts now produce tests that are written and executed consistently

• 29% → 71% of generate tests were acceptable on the first run

• 34% → 79% of tests were debugged and fixed by the agent itself.

Get yourself set up →

• CLAUDE.md snippet, Playwright config, custom command

• Test Enforcing Hook (API key below)

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Yifan

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