Only reset host when app under test is launched.

TestLib/AppleInternals/GREYXCTestAppleInternals.h

@@ -59,3 +59,20 @@
 + (nullable id)sharedClient;
 
 @end
+
+/**
+ * XCTest class representing the active test run's configuration.
+ */
+@interface XCTestConfiguration : NSObject <NSSecureCoding, NSCopying>
+
+/**
+ * Returns the singleton active test configuration instance.
+ */
++ (nonnull instancetype)activeTestConfiguration;
+
+/**
+ * The bundle identifier of the primary application under test.
+ */
+@property(copy, nullable) NSString *targetApplicationBundleID;
+
+@end

TestLib/EarlGreyImpl/XCUIApplication+GREYTest.m

@@ -27,6 +27,7 @@
 #import "GREYLogger.h"
 #import "GREYSetup.h"
 #import "GREYSwizzler.h"
+#import "GREYXCTestAppleInternals.h"
 #import "GREYTestConfiguration.h"
 #import "XCUIApplication+GREYEnvironment.h"
 
@@ -52,36 +53,56 @@ + (NSString *)greyTestRigName {
 - (void)grey_launch {
   [self modifyKeyboardSettings];
 
-  // Setup the Launch Environments.
-  [self grey_configureApplicationForLaunch];
-  // Setup the Launch Arguments for eDO.
-  NSMutableArray<NSString *> *launchArgs = [self.launchArguments mutableCopy];
-  if (!launchArgs) {
-    launchArgs = [[NSMutableArray alloc] init];
-  }
-  GREYTestApplicationDistantObject *testDistantObject =
-      GREYTestApplicationDistantObject.sharedInstance;
-  [launchArgs addObjectsFromArray:@[
-    @"-edoTestPort",
-    @(testDistantObject.servicePort).stringValue,
-    @"-IsRunningEarlGreyTest",
-    @"YES",
-  ]];
-
-  NSString *loggingValue = [NSProcessInfo processInfo].environment[kGREYAllowVerboseLogging];
-  if (loggingValue) {
-    AddVerboseLoggingIfNeeded(launchArgs, loggingValue);
-  }
-  self.launchArguments = launchArgs;
+  static NSString *gPrimaryAppBundleID;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    @try {
+      gPrimaryAppBundleID = XCTestConfiguration.activeTestConfiguration.targetApplicationBundleID;
+    } @catch (NSException *exception) {
+      GREYLog(@"Failed to read targetApplicationBundleID from XCTestConfiguration: %@", exception);
+    }
+  });
 
-  // Reset the port number for the app under test before every -[XCUIApplication launch] call.
-  [testDistantObject resetHostArguments];
+  // It is the primary app under test if the bundleID matches the static target,
+  // or if it is nil/empty (representing the default init rig target).
+  NSString *currentBundleID = self.bundleID;
+  BOOL isAppUnderTest = (gPrimaryAppBundleID.length == 0) || (currentBundleID.length == 0) ||
+                        [gPrimaryAppBundleID isEqualToString:currentBundleID];
+  GREYLog(@"Launching application with bundle identifier: '%@' (app under test: '%@').",
+          currentBundleID, gPrimaryAppBundleID);
+
+  if (isAppUnderTest) {
+    // Setup the Launch Environments.
+    [self grey_configureApplicationForLaunch];
+    // Setup the Launch Arguments for eDO.
+    NSMutableArray<NSString *> *launchArgs = [self.launchArguments mutableCopy];
+    if (!launchArgs) {
+      launchArgs = [[NSMutableArray alloc] init];
+    }
+    GREYTestApplicationDistantObject *testDistantObject =
+        GREYTestApplicationDistantObject.sharedInstance;
+    [launchArgs addObjectsFromArray:@[
+      @"-edoTestPort",
+      @(testDistantObject.servicePort).stringValue,
+      @"-IsRunningEarlGreyTest",
+      @"YES",
+    ]];
+
+    NSString *loggingValue = [NSProcessInfo processInfo].environment[kGREYAllowVerboseLogging];
+    if (loggingValue) {
+      AddVerboseLoggingIfNeeded(launchArgs, loggingValue);
+    }
+    self.launchArguments = launchArgs;
+
+    // Reset the port number for the app under test before every -[XCUIApplication launch] call.
+    [testDistantObject resetHostArguments];
+  }
 
   NSTimer *validTimer = AddTimerForLaunchTimeout();
   INVOKE_ORIGINAL_IMP(void, @selector(grey_launch));
   [validTimer invalidate];
-  // When the identifier is @c nil or empty, it is the TestRig application being launched.
-  if (self.identifier.length == 0) {
+
+  if (isAppUnderTest) {
     objc_setAssociatedObject([XCUIApplication class], @selector(greyTestRigName), self.label,
                              OBJC_ASSOCIATION_RETAIN_NONATOMIC);
   }