Axe

About the CLI

This skill wraps the open-source AXe CLI (https://github.com/cameroncooke/AXe). Keep the local copy aligned to that repo and always target a simulator UDID so the iOS team can rely on consistent simulator automation.

Step 1: Confirm runtime context

1. Identify simulator UDID target first (axe list-simulators).
2. Simulator-interaction AXe commands require --udid <UDID>. Commands like list-simulators and init do not.
3. Run axe describe-ui --udid <UDID> to inspect the current screen. Use the output to discover available --id and --label values for selector taps, and to confirm coordinates for coordinate-based taps.
4. Prefer selector taps (tap --id / tap --label) over raw coordinates. Selectors are resilient to layout changes, work across device sizes, and support element waiting (--wait-timeout) in batch flows.

Step 2: Choose the right command

Available commands: init, tap, swipe, gesture, touch, type, button, key, key-sequence, key-combo, batch, describe-ui, screenshot, record-video, stream-video, list-simulators. Run axe --help or axe <command> --help for full options.

Common examples:

axe tap --id <identifier> --udid <UDID>
axe tap --label <text> --udid <UDID>
axe tap -x <X> -y <Y> --udid <UDID>
axe type 'text' --udid <UDID>
axe describe-ui --udid <UDID>
axe screenshot --udid <UDID> --output screenshot.png

Step 3: Understand the execution model

HID commands (tap, swipe, type, key, etc.) are fire-and-forget — AXe confirms the event was dispatched to the simulator but cannot verify the app actually processed it. A tap may land before a view is interactive, or during a transition. This means:

• Always verify outcomes separately with describe-ui or screenshot.
• Use --wait-timeout in batch to wait for elements to appear, and sleep steps or --pre-delay / --post-delay to allow animations to settle.

Step 4: Apply timing and input best practices

• Use --pre-delay / --post-delay on tap, swipe, and gesture commands for fixed delays around actions.
• Use --duration to control how long a swipe, gesture, button press, or key press lasts.
• For text with shell-sensitive characters, prefer --stdin or --file over inline quotes.
• Use single quotes for inline text arguments to avoid shell expansion issues.

Step 5: Batch vs discrete commands

Prefer axe batch for multi-step flows. Batch executes every step in a single process invocation, which means:

• One tool call and one AI turn instead of many — significantly reduces agent latency and cost.
• A single HID session is reused across all steps, lowering per-step overhead.
• Steps execute sequentially — each step runs before the next is resolved, so earlier taps can trigger navigation and later selector taps will find newly appeared elements (with --wait-timeout).

Fall back to discrete commands when:

• A step's parameters depend on runtime inspection of a previous step's result (e.g. parsing describe-ui JSON to choose coordinates dynamically).

Handling animations and transitions in batch:

• Use --wait-timeout <seconds> so selector taps (--id / --label) poll the accessibility tree until the element appears or the timeout expires. This is the primary mechanism for multi-screen flows.
• Use --poll-interval <seconds> to control polling frequency during waiting (default 0.25s).
• Use --ax-cache perStep when not using --wait-timeout but the UI still changes between steps — this ensures each selector tap gets a fresh accessibility snapshot rather than a stale cached one.
• Insert explicit sleep <seconds> steps when coordinate-based taps need the UI to be stable (selectors with --wait-timeout are preferred over sleep where possible).
• Keep batch output quiet by default. Add --verbose only when troubleshooting.
• If tap --label reports multiple matches and no AXUniqueId values are exposed, fall back to tap -x/-y for that step.

Key rules:

• Use exactly one step source per run: --step, --file, or --stdin.
• Steps run in order; default is fail-fast.
• Add --continue-on-error for best-effort execution.
• Do not pass --udid inside step lines; keep it at batch level.

Step 6: Verify outcomes

Batch and individual commands are execution-focused, not assertion-focused. Always suggest verification when outcomes matter:

axe describe-ui --udid <UDID>
# or
axe screenshot --udid <UDID> --output post-state.png

Step 7: Exit criteria

Before finalising guidance, verify:

• Every simulator-interaction command includes --udid.
• Only valid AXe commands and flags are used.
• Shell quoting is correct (single quotes for literals, --stdin/--file for complex text).
• Verification is suggested as a separate step when results matter.