Fixtures

A fixture is the state your app is in before a check’s steps begin: signed in, a cart with two items, a clean install. You write it once in .mobster/fixtures/ and name it in each check that needs it.

# .mobster/fixtures/signed-in.yaml
launch:
  args: [-UITests]
  env: {API_HOST: staging.example.com}
steps:
  - type ${TEST_EMAIL} into Email
  - type ${TEST_PASSWORD} into Password and tap Sign in

# .mobster/fixtures/logged-in-cart.yaml
extends: signed-in
reset: data
keychain: reset
files:
  - from: files/cart.json        # inside .mobster/fixtures/
    to: Documents/cart.json      # inside the app's data container
pasteboard: SAVE10

# .mobster/checks/checkout.yaml
app: {bundle: com.example.shop}
fixture: logged-in-cart          # or a list: [clean, logged-in-cart]
steps:
  - tap Checkout
expect:
  - text: Order summary

What a fixture holds

Key	What it does	Where
`extends`	Fixtures this one builds on, applied first	Anywhere
`reset`	`none`, `data` or `reinstall`, as in Reset levels. The check’s own `reset` wins	Simulators
`launch.args`, `launch.env`	Added to the check’s. For a name in both, the check’s env wins	Anywhere
`steps`	Run before the check’s steps, such as signing in	Anywhere
`files`	Copied into the app’s data container before it launches. A folder copies whole	Simulators
`keychain: reset`	Empties the simulator’s keychain	Simulators
`pasteboard`	Sets the simulator’s clipboard	Simulators

A sign-in uses the project’s secrets: ${TEST_EMAIL} and ${TEST_PASSWORD} come from mobster env (Checks), are filled in when the run starts, and never reach a report. Fixtures compose in the order you name them. reset and nonempty pasteboard take the last one set. Keychain resets accumulate. args and steps add up. env and a file’s destination are replaced by a later fixture. A fixture used twice runs once, and a circle (a extends b extends a) is refused with the chain.

List and apply

mobster fixtures list

demo-seed: 1 file, keychain reset, pasteboard  [simulators only]
logged-in-cart: reset data, 1 file, keychain reset, pasteboard, 1 arg, 1 env, 2 steps  (builds on signed-in)  [simulators only]
signed-in: 1 arg, 1 env, 2 steps

mobster fixtures apply does the same to a simulator now, without a check: it resets the app, resets the keychain, copies the files and sets the pasteboard. It doesn’t launch the app, and it leaves a fixture’s args, env and steps for a check to use. Run on 18 Oct 2026 on an iPhone 17 Pro simulator (iOS 26.4):

mobster fixtures apply demo-seed --bundle dev.mobster.daybreak --sim "iPhone 17 Pro"

Simulator: Mobster · iPhone 17 Pro · iOS 26.4 · 3
Applied demo-seed to dev.mobster.daybreak on Mobster · iPhone 17 Pro · iOS 26.4 · 3: keychain reset, 1 file copied, pasteboard set.

cat of the file in the app’s container then read {"items": 2}, and xcrun simctl pbpaste read SAVE10. The first run on a simulator also builds WebDriverAgent, which took 92 s that day. --json prints the list as JSON, and GET /api/tests/fixtures?project=/abs/path returns it to the Mac app: each fixture’s flattened reset, args, env, steps, files, keychain, destructive, and whether a pasteboard is set (never its text).

What it won’t do to your iPhone

A reset, seed files, a keychain reset and a pasteboard change a device’s state, so they run on simulators only. A check on a real iPhone whose fixture holds any of them doesn’t run, and says why before it touches the phone:

mobster fixtures: a reset changes the state of a phone, and fixtures do that on simulators only (from signed-in, logged-in-cart). Run the check on a simulator, or use a fixture with only launch args, env and steps on the phone.

On a phone, args, env and steps work, so a sign-in fixture runs there. Files go only inside the app’s data container on a simulator Mobster made. A destination that leaves the container, a symbolic link in the way, a source outside .mobster/fixtures/ and more than 20 MB are refused, and nothing is copied.

Run checks

Automate

Your stack

App Store

Reference

What a fixture holds

List and apply

What it won’t do to your iPhone

​What a fixture holds

​List and apply

​What it won’t do to your iPhone

What a fixture holds

List and apply

What it won’t do to your iPhone