Test a Mac app

Three levels, cheapest first. Each new story gets the cheapest level that can prove its acceptance criteria. A bug fix starts with a test that fails.

Snapshots (build-and-verify skill) prove how it looks. This skill proves how it behaves.

1. Unit tests

Logic lives in a library target (<App>Kit) with no SwiftUI, so tests run without the app.

import Testing
@testable import AppKitCore

@Test("Natural dates", arguments: [("tomorrow 9am", 1, 9), ("next fri", 5, nil)])
func parses(_ phrase: String, dayOffset: Int, hour: Int?) throws {
    let result = try #require(DateParser.parse(phrase, now: .fixed))
    #expect(result.dayOffset == dayOffset)
    #expect(result.hour == hour)
}

swift test --scratch-path ~/Library/Developer/<App>/test-build

• Fix the clock (now: parameter) and the store path in every test.
• A parser that removes text from what the user typed needs at least 20 negative rows: real titles that contain date or time words ("Watch Friday Night Lights"). Add consistency rows for related phrases ("next week" and "next friday"), and a tested way to undo a parsed part.
• Table tests for anything with many cases. Keep the table in docs/research/<topic>.md too, and add a row there before changing behavior. A date parser easily needs 100 rows.

2. Self-test

A launch flag that runs the same functions the UI calls, prints PASS or FAIL per step, and exits 0 or 1:

APP_STORE=/tmp/<App>-self.store ~/Applications/<App>.app/Contents/MacOS/<App> --selftest
# PASS add task
# PASS complete task
# PASS undo

Always point it at a store in /tmp. Never at the user's data.

Checks worth adding to any self-test:

• Every action's Shortcuts title equals its menu title.
• Every SF Symbol name exists (NSImage(systemSymbolName:accessibilityDescription:)).
• Every URL action round-trips.
• For every page: New Item creates a row that is visible and focused on that page. After an action removes the selected row, selection moves to the next row.
• Smoke step: start every background timer, sampler, and observer for a few seconds, then print PASS. It is the only check that catches crashes on background queues.

A single-instance app (menu bar utility) cannot launch a second copy with --selftest. Make it a bridge command instead. Xcode and XcodeGen apps without a library target: see ../build-and-verify/existing-app.md for a test target with no host app.

Key events and menu audit

The self-test can press real keys without computer use:

let event = NSEvent.keyEvent(with: .keyDown, location: .zero, modifierFlags: [],
    timestamp: 0, windowNumber: window.windowNumber, context: nil,
    characters: "\r", charactersIgnoringModifiers: "\r", isARepeat: false, keyCode: 36)!
NSApp.sendEvent(event)                                // Return in the focused list
NSApp.mainMenu?.performKeyEquivalent(with: commandK)  // a menu shortcut

Send events with the flags a real keyboard sends. Arrow keys always carry .numericPad and .function; an event built with modifierFlags: [] passes a check that the real keyboard fails. In app code, compare only the modifiers people hold down:

let held = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
    .subtracting([.numericPad, .function, .capsLock])
if event.keyCode == 124, held.isEmpty { browseInto() }   // → with nothing held

Test typing by typing: send key events through NSApp.sendEvent and check what the field received. Never set the model's text instead. Setting the text skips focus, and a field that never gets the keyboard still passes. Two apps shipped a typing bug this way: letters went to a panel instead of its filter field, and a typed name landed inside the selected placeholder text.

Walk NSApp.mainMenu and check every command's title, key equivalent, modifiers, and symbol against the command map. One loop turns "every action has a menu item and a shortcut" into a check per item.

Focus the list after making the window key (window.makeKey(), then makeFirstResponder(list)). NSApp.sendEvent sends a key event to the key window, so a key event is lost when no window is key. A search field in the toolbar can take focus first, and then list keys and menu items miss the list.

Menu check (from outside)

Do not test SwiftUI menu state from inside the app. Its items carry no action selector, isEnabled updates on SwiftUI's schedule, and the checks fail whenever another app is in front, which is always true while an agent works. In the self-test, check what the commands receive (the selection passed into them) and run the actions the items call.

Check the real menu from outside, through Accessibility, on a seeded test copy. Computer use app_menu works in the background:

1. Nothing selected: To-Do > Complete is reported disabled.
2. Click a row (app_click), then To-Do > Complete: the row is done and the next row is selected (app_screenshot).

Write these steps into the app's CLAUDE.md, so every agent runs them after touching commands.

Runs that never hang

• Quit through NSApp.terminate, with the exit code set in applicationWillTerminate. Close open sheets first, or terminate is refused and the run waits forever.
• Before each run, delete ~/Library/Saved Application State/<bundle id>.savedState. After a crash, the next launch shows a "reopen windows?" alert that blocks every later run with no output. Do not use -ApplePersistenceIgnoreState: SwiftUI then opens no window at all.
• Delete the old test store and its -wal and -shm files before a seeded run. Seed data only fills an empty store.
• Print line-buffered (setvbuf(stdout, nil, _IOLBF, 0)), so a crash keeps the PASS lines before it.

3. Debug bridge

For behavior a self-test cannot reach: global shortcuts, floating panels, window control, permissions, timing. The running app listens for commands and writes its state to a file. Code shape: ../../code/os-integrations/recipes.md (Debug bridge).

swift scripts/<app>ctl.swift status            # writes and prints status.json
swift scripts/<app>ctl.swift windowLeft        # runs an action by name
swift scripts/<app>ctl.swift snapshot:launcher # draws a window to a PNG
swift scripts/<app>ctl.swift captureProbe:/tmp/a.png   # runs, logs timing, cancels

Commands worth adding:

• status: permissions, feature flags, open panels, counts, last error.
• One command per action, by the same name as the menu item and URL.
• snapshot:<window>: captures one of the app's windows with ScreenCaptureKit (code in ../build-and-verify/existing-app.md).
• appearance:light|dark|system: switches the app's appearance for snapshots.
• selftest: the self-test as a command, for an app that is already running.
• <feature>File:<path>: opens an editor or card on a test file, with no clipboard or data change.
• <feature>Probe: runs a slow path and logs the time of each step (see the performance skill).

Compile the bridge in debug builds, or behind a launch flag in release.

4. Computer use

Last resort, for what only a person can do: a real key press in another app, drag and drop from Finder, a permission prompt. See the clone skill for setup. Tell the user to keep off the mouse while it runs. Capture your own window, never the full screen.

Debug output

A GUI app's print is buffered and lost when the process is killed. Write debug lines to stderr (FileHandle.standardError.write) behind an environment flag (APP_DEBUG=1).

Done when every acceptance line of the story maps to a passing test, self-test step, bridge command, or a named manual check, and the bug fix has a test that failed before the fix.