Reduce XCTest permission watchdog CPU usage and make its polling interval tunable

.nx/version-plans/cut-xctest-permission-watchdog-polling.md

@@ -0,0 +1,5 @@
+---
+__default__: patch
+---
+
+The iOS permission-dialog watchdog now uses far less CPU, and its polling interval is tunable via HARNESS_XCTEST_AGENT_TICK_INTERVAL_MS.

apps/playground/rn-harness.config.mjs

@@ -116,6 +116,7 @@ export default {
   defaultRunner: 'android',
   platformReadyTimeout: 300000,
   bridgeTimeout: 120000,
+  testTimeout: 10000,
 
   permissions: true,
   detectNativeCrashes: true,

packages/platform-ios/src/xctest-agent.ts

@@ -25,6 +25,8 @@ const xctestAgentLogger = logger.child('ios-xctest-agent');
 const XCTEST_AGENT_PROJECT_NAME = 'HarnessXCTestAgent';
 const XCTEST_AGENT_SCHEME_NAME = 'HarnessXCTestAgent';
 const XCTEST_AGENT_PORT_ENV = 'HARNESS_XCTEST_AGENT_PORT';
+const XCTEST_AGENT_TICK_INTERVAL_MS_ENV =
+  'HARNESS_XCTEST_AGENT_TICK_INTERVAL_MS';
 const XCTEST_AGENT_TARGET_BUNDLE_ID_ENV =
   'HARNESS_XCTEST_AGENT_TARGET_BUNDLE_ID';
 const XCTEST_AGENT_XCTESTRUN_FILE_ENV = 'HARNESS_IOS_XCTESTRUN_FILE';
@@ -937,13 +939,20 @@ export const createXCTestAgentController = (options: {
   let processTask: Promise<void> | null = null;
 
   const getLaunchEnvironment = (): Record<string, string> => {
+    const tickIntervalMs = getEnvironmentPath(XCTEST_AGENT_TICK_INTERVAL_MS_ENV);
+
     return Object.assign(
       {},
       options.appBundleId
         ? {
             [XCTEST_AGENT_TARGET_BUNDLE_ID_ENV]: options.appBundleId,
           }
         : {},
+      tickIntervalMs
+        ? {
+            [XCTEST_AGENT_TICK_INTERVAL_MS_ENV]: tickIntervalMs,
+          }
+        : {},
       ...capabilities.map(
         (capability) => capability.getLaunchEnvironment?.() ?? {}
       )

packages/platform-ios/xctest-agent/HarnessXCTestAgentUITests/HarnessXCTestAgentUITests.swift

@@ -180,11 +180,24 @@ private final class XCTestAgentHTTPServer {
 final class HarnessXCTestAgentUITests: XCTestCase {
   private enum Environment {
     static let targetBundleIdentifier = "HARNESS_XCTEST_AGENT_TARGET_BUNDLE_ID"
+    static let tickIntervalMs = "HARNESS_XCTEST_AGENT_TICK_INTERVAL_MS"
   }
 
   private enum Constants {
     static let defaultSessionDuration: TimeInterval = 60 * 60
-    static let tickInterval: TimeInterval = 1
+    static let defaultTickInterval: TimeInterval = 1
+  }
+
+  private static func resolveTickInterval() -> TimeInterval {
+    guard
+      let rawValue = ProcessInfo.processInfo.environment[Environment.tickIntervalMs],
+      let milliseconds = Int(rawValue),
+      milliseconds > 0
+    else {
+      return Constants.defaultTickInterval
+    }
+
+    return TimeInterval(milliseconds) / 1000
   }
 
   private let state = HarnessXCTestAgentState(
@@ -194,6 +207,7 @@ final class HarnessXCTestAgentUITests: XCTestCase {
   private let springboard = XCUIApplication(bundleIdentifier: "com.apple.springboard")
   private var capabilities: [AgentCapability] = []
   private var httpServer: XCTestAgentHTTPServer?
+  private let tickInterval = HarnessXCTestAgentUITests.resolveTickInterval()
 
   private func log(_ message: String) {
     NSLog("[HarnessXCTestAgent] %@", message)
@@ -309,7 +323,7 @@ final class HarnessXCTestAgentUITests: XCTestCase {
       }
 
       RunLoop.current.run(
-        until: Date().addingTimeInterval(Constants.tickInterval)
+        until: Date().addingTimeInterval(tickInterval)
       )
     }
 

packages/platform-ios/xctest-agent/HarnessXCTestAgentUITests/PermissionPromptWatchdog.swift

@@ -54,6 +54,14 @@ final class PermissionPromptWatchdog: AgentCapability {
       return
     }
 
+    let guardQuery = springboard.buttons.matching(
+      NSPredicate(format: "label IN %@", Constants.knownPositiveButtonLabels)
+    ).firstMatch
+
+    guard guardQuery.exists else {
+      return
+    }
+
     for label in Constants.knownPositiveButtonLabels {
       let button = springboard.buttons[label].firstMatch