# Stop letting your AI agent test Android apps with screenshots > Source: > Published: 2026-09-24 23:24:13+00:00 I shipped an Android app mostly by pairing with Claude Code. Writing features went fine. Testing them on a real phone did not. When an AI coding agent tests an app on a device, the usual loop is: take a screenshot, look at it, decide where to tap, tap, take another screenshot. Every step sends an image to the model. A 20-step login-and-checkout flow can cost thousands of image tokens, fill the context window, and the agent still sometimes taps the wrong thing. Most of that work doesn't need eyes. "Tap *Sign in*, wait, check that *Home* is on screen" is a text problem. Android can already describe the screen as text: `uiautomator dump` returns every visible node with its text and bounds. So instead of the agent driving the phone step by step, it writes the steps once as JSON: ``` { "name": "Login works", "app": "com.example.app", "steps": [ {"app": "restart"}, {"type": ["Email", "test@example.com"]}, {"type": ["Password", "secret123"]}, {"tap": "Sign in", "exact": true}, {"expect": ["Home"], "wait": 3} ] } ``` and runs it with one command: ``` bash $ python scenario.py scenarios/login.json PASS Login works (5 steps, 12 s) ``` One line back. If a step fails, the runner prints the failing step, what *was* on screen, and saves a screenshot, which is usually enough for the model to fix either the test or the app: ``` ✗ 5 expect: expected ['Home'] (found []); screen: ['Sign in', 'Wrong password', ...] FAIL Login works step 5/5 (9 s) ``` The model only opens a screenshot when a visual decision is actually needed (layout, colours). Most of the code is not the happy path; it's the stuff that broke on real phones: `uiautomator dump` fails during an animation, the old `ui.xml` is still on the device and gets pulled again, so the test "sees" the previous screen. The runner deletes the file on both sides before every dump.`adb input text` sends the whole string at once. Type character by character.`wlan0` has no IP. Add a few lines to your `CLAUDE.md` / `AGENTS.md`: ``` ## Device testing - Never drive the phone step by step with screenshots. Write a scenario in scenarios/.json and run: python scenario.py scenarios/.json | tail -3 - To see the current screen as text: python ui.py dump ``` I ran ~90 scenarios this way on my own app before extracting the runner into its own repo. It's Python standard library + adb, nothing to install on the phone, MIT licensed: [https://github.com/sinangumuskabak-sys/android-scenario-runner](https://github.com/sinangumuskabak-sys/android-scenario-runner) It isn't a replacement for Espresso or Maestro. It's a single file you can hand to an agent so it tests cheaply. Issues and PRs welcome, especially from people on OEM skins I haven't tried.