diff --git a/packages/google_maps_flutter/google_maps_flutter_ios/tool/run_tests.dart b/packages/google_maps_flutter/google_maps_flutter_ios/tool/run_tests.dart
index f86778c0c2a1..f49c29eaf7fe 100644
--- a/packages/google_maps_flutter/google_maps_flutter_ios/tool/run_tests.dart
+++ b/packages/google_maps_flutter/google_maps_flutter_ios/tool/run_tests.dart
@@ -33,45 +33,12 @@ Future<void> main(List<String> args) async {
     p.join(packageRoot.parent.path, 'google_maps_flutter_ios_shared_code'),
   );
 
-  var failed = false;
-  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
-    recursive: true,
-  )) {
-    if (entity is! File) {
-      continue;
-    }
-    final String relativePath = p.relative(
-      entity.path,
-      from: sharedSourceRoot.path,
-    );
-    // The shared source README.md is not part of the shared source of truth,
-    // just an explanation of this source-sharing system.
-    if (relativePath == 'README.md') {
-      continue;
-    }
-
-    // Adjust the paths to account for the package name being part of the
-    // directory structure for Swift packages.
-    final String packagePath = p.join(
-      packageRoot.path,
-      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
-    );
-
-    print('Validating $relativePath');
-    final packageFile = File(packagePath);
-    if (!packageFile.existsSync()) {
-      print('  File $relativePath does not exist in $packageName');
-      failed = true;
-      continue;
-    }
-    final String expectedContents = normalizedFileContents(entity);
-    final String contents = normalizedFileContents(packageFile);
-    if (contents != expectedContents) {
-      print('  File $relativePath does not match expected contents:');
-      await _printDiff(entity, packageFile);
-      failed = true;
-    }
-  }
+  bool passesValidation = await _validatePackageSharedCode(
+    packageRoot,
+    packageName,
+    sharedSourceRoot: sharedSourceRoot,
+    log: true,
+  );
 
   print(
     '\nChecking for unshared source files that are not in '
@@ -85,13 +52,13 @@ Future<void> main(List<String> args) async {
   if (unsharedFiles.isEmpty) {
     print('  No unexpected unshared files.');
   } else {
-    failed = true;
+    passesValidation = false;
     for (final file in unsharedFiles) {
       print('  $file is not shared');
     }
   }
 
-  if (failed) {
+  if (!passesValidation) {
     print('''
 
 If the changes you made should be shared with other copies of the
@@ -105,11 +72,115 @@ approach to sharing as much code as can still be shared.
 
 For more information on the code sharing structure used by this package, see
 the google_maps_flutter_ios_shared_code/README.md file.
-    ''');
+''');
+    exit(1);
+  }
+
+  // If everything else passed, sanity-check the other implementation packages.
+  // Full diff evaluation is done by the copy of this script in each
+  // implementation package, but if someone edits the shared code without
+  // updating the other packages, this will catch it. This is useful both
+  // locally, where people are unlikely to run the tests in every package, and
+  // in CI, where if there are no changes to an implementation package the CI
+  // for that package will be skipped.
+  print('\nChecking other implementation packages...');
+  final failingPackages = <String>[];
+  for (final FileSystemEntity entity in packageRoot.parent.listSync()) {
+    final String packageName = p.basename(entity.path);
+    if (entity is! Directory ||
+        !packageName.startsWith('google_maps_flutter_ios_') ||
+        packageName == 'google_maps_flutter_ios_shared_code') {
+      continue;
+    }
+    if (!await _validatePackageSharedCode(
+      entity,
+      packageName,
+      sharedSourceRoot: sharedSourceRoot,
+      log: false,
+    )) {
+      failingPackages.add(packageName);
+    }
+  }
+
+  if (failingPackages.isEmpty) {
+    print('  No unexpected diffs found.');
+  } else {
+    print('''
+  The following packages do not match the shared source code:
+${failingPackages.map((p) => '    $p').join('\n')}
+
+If you manually synchronized changes to the shared code, you will also need to
+copy those changes to the other implementation packages. In the future, consider
+using sync_shared_files.dart instead of copying changes to the shared source
+manually.
+''');
     exit(1);
   }
 }
 
+/// Validates that the shared code in [packageRoot] matches the shared source of
+/// truth.
+///
+/// Returns true if the package matches the shared source of truth.
+Future<bool> _validatePackageSharedCode(
+  Directory packageRoot,
+  String packageName, {
+  required Directory sharedSourceRoot,
+  required bool log,
+}) async {
+  var hasDiffs = false;
+  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
+    recursive: true,
+  )) {
+    if (entity is! File) {
+      continue;
+    }
+    final String relativePath = p.relative(
+      entity.path,
+      from: sharedSourceRoot.path,
+    );
+    // The shared source README.md is not part of the shared source of truth,
+    // just an explanation of this source-sharing system.
+    if (relativePath == 'README.md') {
+      continue;
+    }
+    // Ignore .DS_Store files, which may be created in the shared source
+    // directory by the OS.
+    if (relativePath.endsWith('.DS_Store')) {
+      continue;
+    }
+
+    // Adjust the paths to account for the package name being part of the
+    // directory structure for Swift packages.
+    final String packagePath = p.join(
+      packageRoot.path,
+      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
+    );
+
+    if (log) {
+      print('Validating $relativePath');
+    }
+    final packageFile = File(packagePath);
+    if (!packageFile.existsSync()) {
+      if (log) {
+        print('  File $relativePath does not exist in $packageName');
+      }
+      hasDiffs = true;
+      continue;
+    }
+    final String expectedContents = normalizedFileContents(entity);
+    final String contents = normalizedFileContents(packageFile);
+    if (contents != expectedContents) {
+      if (log) {
+        print('  File $relativePath does not match expected contents:');
+        await _printDiff(entity, packageFile);
+      }
+      hasDiffs = true;
+    }
+  }
+  return !hasDiffs;
+}
+
 Future<void> _printDiff(File expected, File actual) async {
   final Process process = await Process.start('diff', [
     '-u',
diff --git a/packages/google_maps_flutter/google_maps_flutter_ios_sdk10/tool/run_tests.dart b/packages/google_maps_flutter/google_maps_flutter_ios_sdk10/tool/run_tests.dart
index f86778c0c2a1..f49c29eaf7fe 100644
--- a/packages/google_maps_flutter/google_maps_flutter_ios_sdk10/tool/run_tests.dart
+++ b/packages/google_maps_flutter/google_maps_flutter_ios_sdk10/tool/run_tests.dart
@@ -33,45 +33,12 @@ Future<void> main(List<String> args) async {
     p.join(packageRoot.parent.path, 'google_maps_flutter_ios_shared_code'),
   );
 
-  var failed = false;
-  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
-    recursive: true,
-  )) {
-    if (entity is! File) {
-      continue;
-    }
-    final String relativePath = p.relative(
-      entity.path,
-      from: sharedSourceRoot.path,
-    );
-    // The shared source README.md is not part of the shared source of truth,
-    // just an explanation of this source-sharing system.
-    if (relativePath == 'README.md') {
-      continue;
-    }
-
-    // Adjust the paths to account for the package name being part of the
-    // directory structure for Swift packages.
-    final String packagePath = p.join(
-      packageRoot.path,
-      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
-    );
-
-    print('Validating $relativePath');
-    final packageFile = File(packagePath);
-    if (!packageFile.existsSync()) {
-      print('  File $relativePath does not exist in $packageName');
-      failed = true;
-      continue;
-    }
-    final String expectedContents = normalizedFileContents(entity);
-    final String contents = normalizedFileContents(packageFile);
-    if (contents != expectedContents) {
-      print('  File $relativePath does not match expected contents:');
-      await _printDiff(entity, packageFile);
-      failed = true;
-    }
-  }
+  bool passesValidation = await _validatePackageSharedCode(
+    packageRoot,
+    packageName,
+    sharedSourceRoot: sharedSourceRoot,
+    log: true,
+  );
 
   print(
     '\nChecking for unshared source files that are not in '
@@ -85,13 +52,13 @@ Future<void> main(List<String> args) async {
   if (unsharedFiles.isEmpty) {
     print('  No unexpected unshared files.');
   } else {
-    failed = true;
+    passesValidation = false;
     for (final file in unsharedFiles) {
       print('  $file is not shared');
     }
   }
 
-  if (failed) {
+  if (!passesValidation) {
     print('''
 
 If the changes you made should be shared with other copies of the
@@ -105,11 +72,115 @@ approach to sharing as much code as can still be shared.
 
 For more information on the code sharing structure used by this package, see
 the google_maps_flutter_ios_shared_code/README.md file.
-    ''');
+''');
+    exit(1);
+  }
+
+  // If everything else passed, sanity-check the other implementation packages.
+  // Full diff evaluation is done by the copy of this script in each
+  // implementation package, but if someone edits the shared code without
+  // updating the other packages, this will catch it. This is useful both
+  // locally, where people are unlikely to run the tests in every package, and
+  // in CI, where if there are no changes to an implementation package the CI
+  // for that package will be skipped.
+  print('\nChecking other implementation packages...');
+  final failingPackages = <String>[];
+  for (final FileSystemEntity entity in packageRoot.parent.listSync()) {
+    final String packageName = p.basename(entity.path);
+    if (entity is! Directory ||
+        !packageName.startsWith('google_maps_flutter_ios_') ||
+        packageName == 'google_maps_flutter_ios_shared_code') {
+      continue;
+    }
+    if (!await _validatePackageSharedCode(
+      entity,
+      packageName,
+      sharedSourceRoot: sharedSourceRoot,
+      log: false,
+    )) {
+      failingPackages.add(packageName);
+    }
+  }
+
+  if (failingPackages.isEmpty) {
+    print('  No unexpected diffs found.');
+  } else {
+    print('''
+  The following packages do not match the shared source code:
+${failingPackages.map((p) => '    $p').join('\n')}
+
+If you manually synchronized changes to the shared code, you will also need to
+copy those changes to the other implementation packages. In the future, consider
+using sync_shared_files.dart instead of copying changes to the shared source
+manually.
+''');
     exit(1);
   }
 }
 
+/// Validates that the shared code in [packageRoot] matches the shared source of
+/// truth.
+///
+/// Returns true if the package matches the shared source of truth.
+Future<bool> _validatePackageSharedCode(
+  Directory packageRoot,
+  String packageName, {
+  required Directory sharedSourceRoot,
+  required bool log,
+}) async {
+  var hasDiffs = false;
+  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
+    recursive: true,
+  )) {
+    if (entity is! File) {
+      continue;
+    }
+    final String relativePath = p.relative(
+      entity.path,
+      from: sharedSourceRoot.path,
+    );
+    // The shared source README.md is not part of the shared source of truth,
+    // just an explanation of this source-sharing system.
+    if (relativePath == 'README.md') {
+      continue;
+    }
+    // Ignore .DS_Store files, which may be created in the shared source
+    // directory by the OS.
+    if (relativePath.endsWith('.DS_Store')) {
+      continue;
+    }
+
+    // Adjust the paths to account for the package name being part of the
+    // directory structure for Swift packages.
+    final String packagePath = p.join(
+      packageRoot.path,
+      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
+    );
+
+    if (log) {
+      print('Validating $relativePath');
+    }
+    final packageFile = File(packagePath);
+    if (!packageFile.existsSync()) {
+      if (log) {
+        print('  File $relativePath does not exist in $packageName');
+      }
+      hasDiffs = true;
+      continue;
+    }
+    final String expectedContents = normalizedFileContents(entity);
+    final String contents = normalizedFileContents(packageFile);
+    if (contents != expectedContents) {
+      if (log) {
+        print('  File $relativePath does not match expected contents:');
+        await _printDiff(entity, packageFile);
+      }
+      hasDiffs = true;
+    }
+  }
+  return !hasDiffs;
+}
+
 Future<void> _printDiff(File expected, File actual) async {
   final Process process = await Process.start('diff', [
     '-u',
diff --git a/packages/google_maps_flutter/google_maps_flutter_ios_sdk9/tool/run_tests.dart b/packages/google_maps_flutter/google_maps_flutter_ios_sdk9/tool/run_tests.dart
index f86778c0c2a1..f49c29eaf7fe 100644
--- a/packages/google_maps_flutter/google_maps_flutter_ios_sdk9/tool/run_tests.dart
+++ b/packages/google_maps_flutter/google_maps_flutter_ios_sdk9/tool/run_tests.dart
@@ -33,45 +33,12 @@ Future<void> main(List<String> args) async {
     p.join(packageRoot.parent.path, 'google_maps_flutter_ios_shared_code'),
   );
 
-  var failed = false;
-  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
-    recursive: true,
-  )) {
-    if (entity is! File) {
-      continue;
-    }
-    final String relativePath = p.relative(
-      entity.path,
-      from: sharedSourceRoot.path,
-    );
-    // The shared source README.md is not part of the shared source of truth,
-    // just an explanation of this source-sharing system.
-    if (relativePath == 'README.md') {
-      continue;
-    }
-
-    // Adjust the paths to account for the package name being part of the
-    // directory structure for Swift packages.
-    final String packagePath = p.join(
-      packageRoot.path,
-      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
-    );
-
-    print('Validating $relativePath');
-    final packageFile = File(packagePath);
-    if (!packageFile.existsSync()) {
-      print('  File $relativePath does not exist in $packageName');
-      failed = true;
-      continue;
-    }
-    final String expectedContents = normalizedFileContents(entity);
-    final String contents = normalizedFileContents(packageFile);
-    if (contents != expectedContents) {
-      print('  File $relativePath does not match expected contents:');
-      await _printDiff(entity, packageFile);
-      failed = true;
-    }
-  }
+  bool passesValidation = await _validatePackageSharedCode(
+    packageRoot,
+    packageName,
+    sharedSourceRoot: sharedSourceRoot,
+    log: true,
+  );
 
   print(
     '\nChecking for unshared source files that are not in '
@@ -85,13 +52,13 @@ Future<void> main(List<String> args) async {
   if (unsharedFiles.isEmpty) {
     print('  No unexpected unshared files.');
   } else {
-    failed = true;
+    passesValidation = false;
     for (final file in unsharedFiles) {
       print('  $file is not shared');
     }
   }
 
-  if (failed) {
+  if (!passesValidation) {
     print('''
 
 If the changes you made should be shared with other copies of the
@@ -105,11 +72,115 @@ approach to sharing as much code as can still be shared.
 
 For more information on the code sharing structure used by this package, see
 the google_maps_flutter_ios_shared_code/README.md file.
-    ''');
+''');
+    exit(1);
+  }
+
+  // If everything else passed, sanity-check the other implementation packages.
+  // Full diff evaluation is done by the copy of this script in each
+  // implementation package, but if someone edits the shared code without
+  // updating the other packages, this will catch it. This is useful both
+  // locally, where people are unlikely to run the tests in every package, and
+  // in CI, where if there are no changes to an implementation package the CI
+  // for that package will be skipped.
+  print('\nChecking other implementation packages...');
+  final failingPackages = <String>[];
+  for (final FileSystemEntity entity in packageRoot.parent.listSync()) {
+    final String packageName = p.basename(entity.path);
+    if (entity is! Directory ||
+        !packageName.startsWith('google_maps_flutter_ios_') ||
+        packageName == 'google_maps_flutter_ios_shared_code') {
+      continue;
+    }
+    if (!await _validatePackageSharedCode(
+      entity,
+      packageName,
+      sharedSourceRoot: sharedSourceRoot,
+      log: false,
+    )) {
+      failingPackages.add(packageName);
+    }
+  }
+
+  if (failingPackages.isEmpty) {
+    print('  No unexpected diffs found.');
+  } else {
+    print('''
+  The following packages do not match the shared source code:
+${failingPackages.map((p) => '    $p').join('\n')}
+
+If you manually synchronized changes to the shared code, you will also need to
+copy those changes to the other implementation packages. In the future, consider
+using sync_shared_files.dart instead of copying changes to the shared source
+manually.
+''');
     exit(1);
   }
 }
 
+/// Validates that the shared code in [packageRoot] matches the shared source of
+/// truth.
+///
+/// Returns true if the package matches the shared source of truth.
+Future<bool> _validatePackageSharedCode(
+  Directory packageRoot,
+  String packageName, {
+  required Directory sharedSourceRoot,
+  required bool log,
+}) async {
+  var hasDiffs = false;
+  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
+    recursive: true,
+  )) {
+    if (entity is! File) {
+      continue;
+    }
+    final String relativePath = p.relative(
+      entity.path,
+      from: sharedSourceRoot.path,
+    );
+    // The shared source README.md is not part of the shared source of truth,
+    // just an explanation of this source-sharing system.
+    if (relativePath == 'README.md') {
+      continue;
+    }
+    // Ignore .DS_Store files, which may be created in the shared source
+    // directory by the OS.
+    if (relativePath.endsWith('.DS_Store')) {
+      continue;
+    }
+
+    // Adjust the paths to account for the package name being part of the
+    // directory structure for Swift packages.
+    final String packagePath = p.join(
+      packageRoot.path,
+      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
+    );
+
+    if (log) {
+      print('Validating $relativePath');
+    }
+    final packageFile = File(packagePath);
+    if (!packageFile.existsSync()) {
+      if (log) {
+        print('  File $relativePath does not exist in $packageName');
+      }
+      hasDiffs = true;
+      continue;
+    }
+    final String expectedContents = normalizedFileContents(entity);
+    final String contents = normalizedFileContents(packageFile);
+    if (contents != expectedContents) {
+      if (log) {
+        print('  File $relativePath does not match expected contents:');
+        await _printDiff(entity, packageFile);
+      }
+      hasDiffs = true;
+    }
+  }
+  return !hasDiffs;
+}
+
 Future<void> _printDiff(File expected, File actual) async {
   final Process process = await Process.start('diff', [
     '-u',
diff --git a/packages/google_maps_flutter/google_maps_flutter_ios_shared_code/tool/run_tests.dart b/packages/google_maps_flutter/google_maps_flutter_ios_shared_code/tool/run_tests.dart
index f86778c0c2a1..f49c29eaf7fe 100644
--- a/packages/google_maps_flutter/google_maps_flutter_ios_shared_code/tool/run_tests.dart
+++ b/packages/google_maps_flutter/google_maps_flutter_ios_shared_code/tool/run_tests.dart
@@ -33,45 +33,12 @@ Future<void> main(List<String> args) async {
     p.join(packageRoot.parent.path, 'google_maps_flutter_ios_shared_code'),
   );
 
-  var failed = false;
-  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
-    recursive: true,
-  )) {
-    if (entity is! File) {
-      continue;
-    }
-    final String relativePath = p.relative(
-      entity.path,
-      from: sharedSourceRoot.path,
-    );
-    // The shared source README.md is not part of the shared source of truth,
-    // just an explanation of this source-sharing system.
-    if (relativePath == 'README.md') {
-      continue;
-    }
-
-    // Adjust the paths to account for the package name being part of the
-    // directory structure for Swift packages.
-    final String packagePath = p.join(
-      packageRoot.path,
-      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
-    );
-
-    print('Validating $relativePath');
-    final packageFile = File(packagePath);
-    if (!packageFile.existsSync()) {
-      print('  File $relativePath does not exist in $packageName');
-      failed = true;
-      continue;
-    }
-    final String expectedContents = normalizedFileContents(entity);
-    final String contents = normalizedFileContents(packageFile);
-    if (contents != expectedContents) {
-      print('  File $relativePath does not match expected contents:');
-      await _printDiff(entity, packageFile);
-      failed = true;
-    }
-  }
+  bool passesValidation = await _validatePackageSharedCode(
+    packageRoot,
+    packageName,
+    sharedSourceRoot: sharedSourceRoot,
+    log: true,
+  );
 
   print(
     '\nChecking for unshared source files that are not in '
@@ -85,13 +52,13 @@ Future<void> main(List<String> args) async {
   if (unsharedFiles.isEmpty) {
     print('  No unexpected unshared files.');
   } else {
-    failed = true;
+    passesValidation = false;
     for (final file in unsharedFiles) {
       print('  $file is not shared');
     }
   }
 
-  if (failed) {
+  if (!passesValidation) {
     print('''
 
 If the changes you made should be shared with other copies of the
@@ -105,11 +72,115 @@ approach to sharing as much code as can still be shared.
 
 For more information on the code sharing structure used by this package, see
 the google_maps_flutter_ios_shared_code/README.md file.
-    ''');
+''');
+    exit(1);
+  }
+
+  // If everything else passed, sanity-check the other implementation packages.
+  // Full diff evaluation is done by the copy of this script in each
+  // implementation package, but if someone edits the shared code without
+  // updating the other packages, this will catch it. This is useful both
+  // locally, where people are unlikely to run the tests in every package, and
+  // in CI, where if there are no changes to an implementation package the CI
+  // for that package will be skipped.
+  print('\nChecking other implementation packages...');
+  final failingPackages = <String>[];
+  for (final FileSystemEntity entity in packageRoot.parent.listSync()) {
+    final String packageName = p.basename(entity.path);
+    if (entity is! Directory ||
+        !packageName.startsWith('google_maps_flutter_ios_') ||
+        packageName == 'google_maps_flutter_ios_shared_code') {
+      continue;
+    }
+    if (!await _validatePackageSharedCode(
+      entity,
+      packageName,
+      sharedSourceRoot: sharedSourceRoot,
+      log: false,
+    )) {
+      failingPackages.add(packageName);
+    }
+  }
+
+  if (failingPackages.isEmpty) {
+    print('  No unexpected diffs found.');
+  } else {
+    print('''
+  The following packages do not match the shared source code:
+${failingPackages.map((p) => '    $p').join('\n')}
+
+If you manually synchronized changes to the shared code, you will also need to
+copy those changes to the other implementation packages. In the future, consider
+using sync_shared_files.dart instead of copying changes to the shared source
+manually.
+''');
     exit(1);
   }
 }
 
+/// Validates that the shared code in [packageRoot] matches the shared source of
+/// truth.
+///
+/// Returns true if the package matches the shared source of truth.
+Future<bool> _validatePackageSharedCode(
+  Directory packageRoot,
+  String packageName, {
+  required Directory sharedSourceRoot,
+  required bool log,
+}) async {
+  var hasDiffs = false;
+  for (final FileSystemEntity entity in sharedSourceRoot.listSync(
+    recursive: true,
+  )) {
+    if (entity is! File) {
+      continue;
+    }
+    final String relativePath = p.relative(
+      entity.path,
+      from: sharedSourceRoot.path,
+    );
+    // The shared source README.md is not part of the shared source of truth,
+    // just an explanation of this source-sharing system.
+    if (relativePath == 'README.md') {
+      continue;
+    }
+    // Ignore .DS_Store files, which may be created in the shared source
+    // directory by the OS.
+    if (relativePath.endsWith('.DS_Store')) {
+      continue;
+    }
+
+    // Adjust the paths to account for the package name being part of the
+    // directory structure for Swift packages.
+    final String packagePath = p.join(
+      packageRoot.path,
+      packageRelativePathForSharedSourceRelativePath(packageName, relativePath),
+    );
+
+    if (log) {
+      print('Validating $relativePath');
+    }
+    final packageFile = File(packagePath);
+    if (!packageFile.existsSync()) {
+      if (log) {
+        print('  File $relativePath does not exist in $packageName');
+      }
+      hasDiffs = true;
+      continue;
+    }
+    final String expectedContents = normalizedFileContents(entity);
+    final String contents = normalizedFileContents(packageFile);
+    if (contents != expectedContents) {
+      if (log) {
+        print('  File $relativePath does not match expected contents:');
+        await _printDiff(entity, packageFile);
+      }
+      hasDiffs = true;
+    }
+  }
+  return !hasDiffs;
+}
+
 Future<void> _printDiff(File expected, File actual) async {
   final Process process = await Process.start('diff', [
     '-u',