Maestro vs XCUITest vs Mobster: when to use which

Three tools check iOS screens, and they start from different places. XCUITest is Apple’s framework: tests are Swift code inside your Xcode project. Maestro is a cross-platform test runner: flows are YAML files of commands. Mobster is built for apps a coding agent helps write: the agent drives your app through MCP tools, and the verdict comes from assertions fixed before it started. If an agent writes your screens, pick Mobster. We make Mobster; the facts about the other two come from their own docs, read on 8 October 2026.

The three side by side

Mobster vs Maestro, Mobster vs XCUITest and Mobster vs Appium go row by row, with the sources.

Pick Mobster when a coding agent writes your screens

The agent proves the screen it wrote. It builds your app for the simulator and calls verify_start with the steps and what must be true. Then it drives with screen, tap, type_text and swipe, each of which returns the new screen as an outline of the accessibility tree, and calls verify_finish. Mobster checks the assertions on one settled read and returns the verdict with an overlay frame. The expectations are fixed before the agent touches the app, so it can’t bend them to fit what it finds. Test your iOS app with Codex walks through the loop.

No model in the verdict. A Mobster check passes when every assertion holds on one settled screen. A check whose assertions already held before the steps ran ends needs_review, because it doesn’t prove the flow works. What a model says about its own run is never an input. AI end-to-end tests for iOS explains the rules.

Checks anyone can read. A check is the steps in plain English and a list of what must be true, in a YAML file you commit. An agent performs the steps, so they survive a renamed button or a new screen in the middle. Any run becomes a check with --save, or save_check from your agent. The Checks reference has the format.

The real iPhone too. mobster verify --device checks an app you installed on your USB iPhone without clearing its data. Mobster for Mac builds, signs and renews the runner for each phone.

Simulators you never manage. Mobster creates its own simulators, boots them headless, builds WebDriverAgent once per Xcode version and resets the app before each run. It leaves your own simulators alone.

Pick XCUITest or Maestro for these jobs

• XCUITest for a regression suite that compiles with your app and runs with xcodebuild test in any CI or in Xcode Cloud, written as Swift code.
• Maestro for one suite across Android, iOS simulators and the web, or for a hosted device cloud ($250 per device a month on Maestro Cloud, with a free trial).

They work together

XCUITest in CI, Mobster in the agent’s loop. Keep the suite you have. Let the agent check each screen it changes with Mobster before it opens a pull request, and let CI run XCUITest on the result. Both find elements by accessibility identifier, so .accessibilityIdentifier("plan_annual") in SwiftUI serves both.

Maestro for cross-platform regression, Mobster for the iPhone. Maestro covers the cross-platform suite on simulators and emulators. Mobster covers what needs a real iPhone, and the agent’s loop on iOS.

A first Mobster check

Daybreak, the sample app in Mobster’s repository, has a paywall with three plans and a script that plants a bug. The quick start, run on 28 September 2026 with the missing-plan bug planted, printed this:

✗ failed  The paywall shows three plans with Annual at $39.99 a year  (18.2 s)
  ✓ text "Choose your plan"
  ✗ count id=/^plan_/ == 3: found 2: plan_weekly, plan_monthly
  ✗ value id=plan_annual == "$39.99 / year": not found; closest: "plan_monthly"
  ✓ visible label=Restore Purchases role=button
  ✓ no_text "Loading"

Without the bug it exits 0.

$ curl -fsSL https://mobster.dev/install.sh | sh
$ mobster sim doctor --fix
$ git clone https://github.com/RadishSoftware/mobster && cd mobster-cli
$ xcodebuild -project examples/ios/Daybreak/Daybreak.xcodeproj -scheme Daybreak \
  -destination 'generic/platform=iOS Simulator' -derivedDataPath examples/ios/Daybreak/.build CODE_SIGNING_ALLOWED=NO build
$ cd examples/ios/Daybreak
$ mobster verify --check .mobster/checks/paywall.yaml

Getting started with verify does the same with your own app. Mobster’s side here is the build of 8 October 2026, tested on an iPhone 15 Pro running iOS 26 and on iOS 26 simulators.