diff --git a/GoogleSignIn/Sources/GIDEMMErrorHandler.h b/GoogleSignIn/Sources/GIDEMMErrorHandler.h
index 5051f56e..9f7ef71c 100644
--- a/GoogleSignIn/Sources/GIDEMMErrorHandler.h
+++ b/GoogleSignIn/Sources/GIDEMMErrorHandler.h
@@ -18,20 +18,38 @@
 #if TARGET_OS_IOS && !TARGET_OS_MACCATALYST
 
 #import <Foundation/Foundation.h>
+#import <UIKit/UIKit.h>
+
+#import "GoogleSignIn/Sources/GIDApplication/API/GIDApplication.h"
+#import "GoogleSignIn/Sources/GIDEMMAlertPresenter/API/GIDEMMAlertPresenter.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
-// The handler for displaying EMM-specific errors to users.
+/// The handler for displaying EMM-specific errors to users.
 @interface GIDEMMErrorHandler : NSObject
 
-// Retrieve the shared instance of this class.
+/// Returns the shared instance of this class.
 + (instancetype)sharedInstance;
 
-// Handles EMM-specific errors in the server |response|. |completion| is always called
-// exactly once, asynchronously on the main thread, with |YES| if |response| carries an EMM
-// error and |NO| otherwise. For an EMM error, a remediation dialog is presented and
-// |completion| is called after the user dismisses it — unless another EMM dialog is already
-// pending or no dialog can be presented, in which case it is called as soon as possible.
+/// Creates a handler that finds the key window and opens URLs through `application`, and shows its
+/// alerts through `alertPresenter`.
+- (instancetype)initWithApplication:(id<GIDApplication>)application
+                     alertPresenter:(id<GIDEMMAlertPresenter>)alertPresenter
+    NS_DESIGNATED_INITIALIZER;
+
+/// Creates a handler backed by `UIApplication.sharedApplication` and a
+/// `GIDEMMAlertWindowPresenter`.
+- (instancetype)init;
+
+/// Returns the application's key window, or nil if there is none.
+/// Exposed for the unit tests.
+- (nullable UIWindow *)keyWindow;
+
+/// Handles EMM-specific errors in the server |response|. |completion| is always called
+/// exactly once, asynchronously on the main thread, with |YES| if |response| carries an EMM
+/// error and |NO| otherwise. For an EMM error, a remediation dialog is presented and
+/// |completion| is called after the user dismisses it — unless another EMM dialog is already
+/// pending or no dialog can be presented, in which case it is called as soon as possible.
 - (void)handleErrorFromResponse:(NSDictionary<NSString *, id> *)response
                      completion:(void (^)(BOOL handled))completion;
 
diff --git a/GoogleSignIn/Sources/GIDEMMErrorHandler.m b/GoogleSignIn/Sources/GIDEMMErrorHandler.m
index 019d6136..f6ef6888 100644
--- a/GoogleSignIn/Sources/GIDEMMErrorHandler.m
+++ b/GoogleSignIn/Sources/GIDEMMErrorHandler.m
@@ -19,6 +19,8 @@
 
 #import <UIKit/UIKit.h>
 
+#import "GoogleSignIn/Sources/GIDApplication/Implementation/GIDSharedApplication.h"
+#import "GoogleSignIn/Sources/GIDEMMAlertPresenter/Implementation/GIDEMMAlertWindowPresenter.h"
 #import "GoogleSignIn/Sources/GIDSignInStrings.h"
 
 NS_ASSUME_NONNULL_BEGIN
@@ -43,6 +45,10 @@
 } ErrorCode;
 
 @implementation GIDEMMErrorHandler {
+  // Finds the key window and opens URLs.
+  id<GIDApplication> _application;
+  // Shows and hides the remediation alert.
+  id<GIDEMMAlertPresenter> _alertPresenter;
   // Whether or not a dialog is pending user interaction.
   BOOL _pendingDialog;
 }
@@ -56,6 +62,21 @@ + (instancetype)sharedInstance {
   return sharedInstance;
 }
 
+- (instancetype)initWithApplication:(id<GIDApplication>)application
+                     alertPresenter:(id<GIDEMMAlertPresenter>)alertPresenter {
+  self = [super init];
+  if (self) {
+    _application = application;
+    _alertPresenter = alertPresenter;
+  }
+  return self;
+}
+
+- (instancetype)init {
+  return [self initWithApplication:[[GIDSharedApplication alloc] init]
+                    alertPresenter:[[GIDEMMAlertWindowPresenter alloc] init]];
+}
+
 - (void)handleErrorFromResponse:(NSDictionary<NSString *, id> *)response
                      completion:(void (^)(BOOL handled))completion {
   ErrorCode errorCode = ErrorCodeNone;
@@ -119,26 +140,8 @@ - (void)handleErrorFromResponse:(NSDictionary<NSString *, id> *)response
       completion(YES);
       return;
     }
-    UIWindow *alertWindow;
-    if (@available(iOS 13, *)) {
-      if (keyWindow.windowScene) {
-        alertWindow = [[UIWindow alloc] initWithWindowScene:keyWindow.windowScene];
-      }
-    }
-    if (!alertWindow) {
-      CGRect keyWindowBounds = CGRectIsEmpty(keyWindow.bounds) ?
-        keyWindow.bounds : [UIScreen mainScreen].bounds;
-      alertWindow = [[UIWindow alloc] initWithFrame:keyWindowBounds];
-    }
-    alertWindow.backgroundColor = [UIColor clearColor];
-    alertWindow.rootViewController = [[UIViewController alloc] init];
-    alertWindow.rootViewController.view.backgroundColor = [UIColor clearColor];
-    alertWindow.windowLevel = UIWindowLevelAlert;
-    [alertWindow makeKeyAndVisible];
     void (^finish)(void) = ^{
-      alertWindow.hidden = YES;
-      alertWindow.rootViewController = nil;
-      [keyWindow makeKeyAndVisible];
+      [self->_alertPresenter dismissAlert];
       clearPendingDialog();
       completion(YES);
     };
@@ -157,7 +160,7 @@ - (void)handleErrorFromResponse:(NSDictionary<NSString *, id> *)response
         break;
     }
     if (alert) {
-      [alertWindow.rootViewController presentViewController:alert animated:YES completion:nil];
+      [self->_alertPresenter presentAlert:alert overKeyWindow:keyWindow];
     } else {
       // Should not happen but just in case.
       finish();
@@ -167,32 +170,7 @@ - (void)handleErrorFromResponse:(NSDictionary<NSString *, id> *)response
 
 // This method is exposed to the unit test.
 - (nullable UIWindow *)keyWindow {
-#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 150000
-  if (@available(iOS 15, *)) {
-    for (UIScene *scene in UIApplication.sharedApplication.connectedScenes) {
-      if ([scene isKindOfClass:[UIWindowScene class]] &&
-          scene.activationState == UISceneActivationStateForegroundActive) {
-        return ((UIWindowScene *)scene).keyWindow;
-      }
-    }
-  } else
-#endif  // __IPHONE_OS_VERSION_MAX_ALLOWED >= 150000
-  {
-#if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_15_0
-    if (@available(iOS 13, *)) {
-      for (UIWindow *window in UIApplication.sharedApplication.windows) {
-        if (window.isKeyWindow) {
-          return window;
-        }
-      }
-    } else {
-#if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_13_0
-      return UIApplication.sharedApplication.keyWindow;
-#endif  // __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_13_0
-    }
-#endif  // __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_15_0
-  }
-  return nil;
+  return [_application keyWindow];
 }
 
 #pragma mark - Alerts
@@ -286,7 +264,7 @@ - (UIAlertController *)appVerificationRequiredAlertWithURL:(nullable NSURL *)url
 }
 
 - (void)openURL:(NSURL *)url {
-  [UIApplication.sharedApplication openURL:url options:@{} completionHandler:nil];
+  [_application openURL:url];
 }
 
 #pragma mark - Localization