IOS Sim Navigation

iOS Simulator Navigation with WebDriverAgent

Drive an explicitly identified app on a user-identified Simulator through one explicitly identified WDA session.

Required navigation target

Retain these values in working context throughout the flow:

• <UDID>: resolve the Simulator identified by the user or established earlier in the task to its exact UDID. If the target cannot be determined unambiguously, ask the user which Simulator to use.
• <BUNDLE_ID>: use the bundle ID established earlier in the task, or resolve it from the app explicitly identified by the user. If the target app cannot be determined unambiguously, ask the user which app to use. Never choose an app merely because it is installed, running, or in the foreground.
• <PORT>: choose a random port from 8200 through 8999. If unavailable, choose another and retry.
• <SESSION_ID>: the exact value printed by wda-session.rb.

Pass <PORT> and <SESSION_ID> explicitly to every WDA action. Keep using the resolved <UDID> and <BUNDLE_ID> throughout the flow.

Fast-path cadence

End-to-end runs have a limited time budget. Keep each user-visible action to about one tool call.

Rule 1: Use tap.rb for every tap

tap.rb validates the supplied session, finds the element, computes its coordinates, taps it, and can wait for the next screen in one invocation:

ruby scripts/tap.rb aid create-post-button \
  --port <PORT> --session-id <SESSION_ID> \
  --wait-aid post-title-field

Use raw curl only for gestures that the scripts do not model.

Rule 2: Never read a screenshot into model context

Use the accessibility tree to make decisions. Screenshots are failure artifacts for human review only. Never read /tmp/*.png back into context.

Rule 3: Fetch one tree per screen

Fetch the description tree once on a new screen, locate the controls you need, then use the action scripts. Re-fetch only after reaching another screen or when an expected transition times out.

curl -s "http://localhost:<PORT>/session/<SESSION_ID>/source?format=description" \
  | jq -r .value

Before starting WDA

Verify that:

• <UDID> identifies a booted Simulator.
• The app identified by <BUNDLE_ID> is installed on that Simulator.

WDA lifecycle

Run wda-start.rb with both required options:

ruby scripts/wda-start.rb --udid <UDID> --port <PORT>

Run that command using the coding environment's tracked background-command facility. Retain the returned task or terminal identifier. Do not append &, use nohup, or detach it another way.

Startup may take several minutes on first use. Poll the selected port until WDA is ready:

curl -sf "http://localhost:<PORT>/status" >/dev/null

The script handles setup and one recovery attempt internally. If startup reports that the port is occupied, choose another random port from 8200 through 8999 and retry. If the background task exits for another reason, inspect its output and report the failure. Do not restart it automatically.

When navigation finishes, stop the exact background task using its retained identifier. Do not scan for WDA processes or stop unrelated background tasks. No additional cleanup command is required.

Create the app session

Create a session before every navigation flow. Both options are required:

ruby scripts/wda-session.rb --port <PORT> --bundle <BUNDLE_ID>

The command prints only the session ID to stdout. Retain that exact value as <SESSION_ID> and pass it to every subsequent action.

Creating the session launches or relaunches the app and binds WDA to it. Do not substitute simctl launch, because a later WDA session can relaunch the app and discard caller-supplied launch configuration.

For launch arguments or environment variables, add repeatable options to the same session command:

ruby scripts/wda-session.rb --port <PORT> --bundle <BUNDLE_ID> \
  --arg -some-flag --arg value

ruby scripts/wda-session.rb --port <PORT> --bundle <BUNDLE_ID> \
  --env SOME_INSTRUMENT_VAR=1

--wait-quiescence is off by default because a spinner can prevent an app from becoming quiescent. If a session becomes invalid, create a new session explicitly and use its new ID. Action scripts never replace sessions silently.

See references/sessions.md for session details.

Tap

Use one of three locators:

# Developer-assigned accessibility identifier (preferred).
ruby scripts/tap.rb aid settings-button \
  --port <PORT> --session-id <SESSION_ID>

# Visible label or accessibility identifier.
ruby scripts/tap.rb text "Continue" \
  --port <PORT> --session-id <SESSION_ID>

# Coordinates, only when no stable identifier or label exists.
ruby scripts/tap.rb at 196,504 \
  --port <PORT> --session-id <SESSION_ID>

Fuse tap and transition verification

Use --wait-aid or --wait-text whenever you can name an element expected on the destination screen:

ruby scripts/tap.rb aid tabbar_mysites \
  --port <PORT> --session-id <SESSION_ID> \
  --wait-aid switch-site-button

ruby scripts/tap.rb text "Continue" \
  --port <PORT> --session-id <SESSION_ID> \
  --wait-text "My Site"

ruby scripts/tap.rb aid publish-button \
  --port <PORT> --session-id <SESSION_ID> \
  --wait-text "Post published" --timeout 15

The wait polls /elements every 250 ms. --wait-aid uses the stable accessibility identifier. --wait-text uses exact equality against label or identifier.

Exit codes:

• 0: tap and optional wait succeeded.
• 1: target missing or wait timed out.
• 2: invalid options, WDA unavailable, or session invalid.

Accessibility tree

Use description format by default:

curl -s "http://localhost:<PORT>/session/<SESSION_ID>/source?format=description" \
  | jq -r .value

Each line contains type, frame, identifier, label, and other useful state. Find elements in this order:

1. Developer-assigned identifier or name.
2. Accessibility label.
3. Type plus surrounding context.
4. Partial text matching.
5. Position, only as a last resort.

For programmatic tree walking, read references/json-tree.md.

Verify step success

Verify presence through the explicit session:

curl -s -X POST \
  "http://localhost:<PORT>/session/<SESSION_ID>/elements" \
  -H 'Content-Type: application/json' \
  -d '{"using":"accessibility id","value":"post-published-banner"}' \
  | jq -e '.value | length > 0'

Verify visible text with one tree dump:

curl -s "http://localhost:<PORT>/session/<SESSION_ID>/source?format=description" \
  | jq -r .value \
  | grep -F "Category tag post"

Prefer adding a wait to the tap that triggers a confirmation. Capture a screenshot only after verification fails, and do not read the image back.

Swipe

Use swipe.rb for every swipe:

ruby scripts/swipe.rb up --port <PORT> --session-id <SESSION_ID>
ruby scripts/swipe.rb down --port <PORT> --session-id <SESSION_ID>
ruby scripts/swipe.rb left --port <PORT> --session-id <SESSION_ID>
ruby scripts/swipe.rb right --port <PORT> --session-id <SESSION_ID>
ruby scripts/swipe.rb back --port <PORT> --session-id <SESSION_ID>

ruby scripts/swipe.rb at 196,500,196,200 \
  --port <PORT> --session-id <SESSION_ID>

ruby scripts/swipe.rb up \
  --port <PORT> --session-id <SESSION_ID> --duration 1000

Directional swipes derive coordinates from the session's window size. Vertical swipes use the right edge to avoid interactive controls in the center.

Scroll view navigation

1. Fetch the tree and look for the target.
2. Tap it if found.
3. Otherwise swipe up and fetch the tree again.
4. Stop when the tree is unchanged after a swipe, which indicates the end.
5. Report element-not-found if the target never appears.

Type text

Use type.rb for every typing action. It finds the field, taps it, waits for the keyboard, types, and verifies the exposed value or label:

ruby scripts/type.rb aid post-title --text "Hello world" \
  --port <PORT> --session-id <SESSION_ID>

ruby scripts/type.rb text "Email" --text "user@example.com" \
  --port <PORT> --session-id <SESSION_ID>

Use --no-verify only when the field genuinely does not expose typed text. Use --no-focus when the field is already focused:

ruby scripts/type.rb aid post-title --text "Hello world" \
  --port <PORT> --session-id <SESSION_ID> --no-focus

Do not use hasKeyboardFocus; iOS 26 rejects it. The valid attribute is focused. Do not tree-dump between characters or after successful verification.

See references/raw-actions.md for control-code typing and clear-field details.

Back navigation

Find the Button inside the NavigationBar and tap its label. If no stable button exists, use the back swipe:

ruby scripts/swipe.rb back --port <PORT> --session-id <SESSION_ID>

Screenshots

Screenshots are failure artifacts for human review only. Use the resolved UDID:

xcrun simctl io <UDID> screenshot /tmp/screenshot.png

Do not re-resolve or switch the screenshot target after <UDID> is established, and never read the resulting PNG into model context.

Reference files