Update UserManagerImpl::UserLoggedIn condition.

The condition to check whether or not multi-sign-in is updated.
Some assumption that UserManagerImpl has is not explicit assertion
with CHECK.

This is preparation to switch Fake{,Chrome}UserManager into
UserManagerImpl.

BUG=278643115
TEST=tryjob

Change-Id: I80d47a588dc8dbec1fb93cd27008b0ddaf0e9eee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6196999
Commit-Queue: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1412459}

chrome/browser/ash/file_manager/external_filesystem_apitest.cc

@@ -36,6 +36,7 @@
 #include "chromeos/ash/components/browser_context_helper/browser_context_types.h"
 #include "components/media_router/browser/test/mock_media_router.h"
 #include "components/session_manager/core/session_manager.h"
+#include "components/user_manager/test_helper.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/navigation_handle.h"
 #include "content/public/test/browser_test.h"
@@ -466,14 +467,26 @@ class MultiProfileDriveFileSystemExtensionApiTest
                                     "false");
   }
 
+  void SetUpLocalStatePrefService(PrefService* local_state) override {
+    InProcessBrowserTest::SetUpLocalStatePrefService(local_state);
+
+    // Register persisted users.
+    user_manager::TestHelper::RegisterPersistedUser(
+        *local_state,
+        AccountId::FromUserEmailGaiaId("testuser@gmail.com", GaiaId("123456")));
+    user_manager::TestHelper::RegisterPersistedUser(
+        *local_state, AccountId::FromUserEmailGaiaId(kSecondProfileAccount,
+                                                     kSecondProfileGaiaId));
+  }
+
   void SetUpOnMainThread() override {
+    // Set up the secondary user session.
     base::FilePath user_data_directory;
     base::PathService::Get(chrome::DIR_USER_DATA, &user_data_directory);
     session_manager::SessionManager::Get()->CreateSession(
         AccountId::FromUserEmailGaiaId(kSecondProfileAccount,
                                        kSecondProfileGaiaId),
         kSecondProfileHash, false);
-    // Set up the secondary profile.
     base::FilePath profile_dir = user_data_directory.AppendASCII(
         ash::BrowserContextHelper::GetUserBrowserContextDirName(
             kSecondProfileHash));

chrome/browser/ash/login/shill_profile_loading_browsertest.cc

@@ -35,6 +35,7 @@
 #include "chromeos/ash/components/login/auth/public/user_context.h"
 #include "components/account_id/account_id.h"
 #include "components/policy/proto/chrome_settings.pb.h"
+#include "components/user_manager/test_helper.h"
 #include "components/user_manager/user_names.h"
 #include "content/public/test/browser_test.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ -105,6 +106,18 @@ class ShillProfileLoadingTest : public LoginManagerTest {
   ~ShillProfileLoadingTest() override = default;
 
   // LoginManagerTest:
+  void SetUpLocalStatePrefService(PrefService* local_state) override {
+    LoginManagerTest::SetUpLocalStatePrefService(local_state);
+
+    // Register a persisted user.
+    user_manager::TestHelper::RegisterPersistedUser(*local_state,
+                                                    unmanaged_user_.account_id);
+    user_manager::TestHelper::RegisterPersistedUser(
+        *local_state, secondary_unmanaged_user_.account_id);
+    user_manager::TestHelper::RegisterPersistedUser(*local_state,
+                                                    managed_user_.account_id);
+  }
+
   void SetUpInProcessBrowserTestFixture() override {
     LoginManagerTest::SetUpInProcessBrowserTestFixture();
 

chrome/browser/ash/login/users/user_manager_unittest.cc

@@ -48,6 +48,7 @@
 #include "components/prefs/pref_service.h"
 #include "components/user_manager/known_user.h"
 #include "components/user_manager/scoped_user_manager.h"
+#include "components/user_manager/test_helper.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_manager_impl.h"
 #include "components/user_manager/user_manager_pref_names.h"
@@ -514,10 +515,17 @@ TEST_F(UserManagerTest, RemoveUser) {
                               false /* browser_restart */,
                               false /* is_child */);
 
+  // Recreate the user manager to log out all accounts.
+  ResetUserManager();
+
   // Create non-owner account  and login in.
   user_manager_->UserLoggedIn(kAccountId0, kAccountId0.GetUserEmail(),
                               false /* browser_restart */,
                               false /* is_child */);
+  // Log-in owner account.
+  user_manager_->UserLoggedIn(kOwnerAccountId, kOwnerAccountId.GetUserEmail(),
+                              false /* browser_restart */,
+                              false /* is_child */);
 
   ASSERT_EQ(2U, user_manager_->GetUsers().size());
 

chrome/browser/ash/scalable_iph/scalable_iph_browser_test_base.cc

@@ -124,6 +124,18 @@ void ScalableIphBrowserTestBase::SetUp() {
   CustomizableTestEnvBrowserTestBase::SetUp();
 }
 
+void ScalableIphBrowserTestBase::SetUpInProcessBrowserTestFixture() {
+  CustomizableTestEnvBrowserTestBase::SetUpInProcessBrowserTestFixture();
+
+  if (enable_multi_user_) {
+    // Add a secondary user.
+    LoginManagerMixin* login_manager_mixin = GetLoginManagerMixin();
+    CHECK(login_manager_mixin);
+    login_manager_mixin->AppendRegularUsers(1);
+    CHECK_EQ(login_manager_mixin->users().size(), 2ul);
+  }
+}
+
 // `SetUpOnMainThread` is called just before a test body. Do the mock set up in
 // this function as `browser()` is not available in `SetUp` above.
 void ScalableIphBrowserTestBase::SetUpOnMainThread() {
@@ -150,12 +162,6 @@ void ScalableIphBrowserTestBase::SetUpOnMainThread() {
   }
 
   if (enable_multi_user_) {
-    // Add a secondary user.
-    LoginManagerMixin* login_manager_mixin = GetLoginManagerMixin();
-    CHECK(login_manager_mixin);
-    login_manager_mixin->AppendRegularUsers(1);
-    CHECK_EQ(login_manager_mixin->users().size(), 2ul);
-
     // By default, `MultiUserWindowManager` is created with multi profile off.
     // Re-create for multi profile tests. This has to be done after
     // `SetUpOnMainThread` of a base class as the original multi-profile-off

chrome/browser/ash/scalable_iph/scalable_iph_browser_test_base.h

@@ -56,6 +56,7 @@ class ScalableIphBrowserTestBase : public CustomizableTestEnvBrowserTestBase {
 
   // CustomizableTestEnvBrowserTestBase:
   void SetUp() override;
+  void SetUpInProcessBrowserTestFixture() override;
   void SetUpOnMainThread() override;
   void TearDownOnMainThread() override;
 

chrome/browser/download/notification/download_notification_browsertest.cc

@@ -70,19 +70,15 @@
 #if BUILDFLAG(IS_CHROMEOS_ASH)
 #include "ash/constants/ash_features.h"
 #include "ash/constants/ash_switches.h"
+#include "components/prefs/scoped_user_pref_update.h"
 #include "components/user_manager/user_manager.h"
+#include "components/user_manager/user_manager_pref_names.h"
 #elif BUILDFLAG(IS_CHROMEOS_LACROS)
 #include "chromeos/startup/browser_init_params.h"
 #endif
 
 namespace {
 
-enum {
-  DUMMY_ACCOUNT_INDEX = 0,
-  PRIMARY_ACCOUNT_INDEX = 1,
-  SECONDARY_ACCOUNT_INDEX_START = 2,
-};
-
 #if BUILDFLAG(IS_CHROMEOS_ASH)
 // Structure to describe an account info.
 struct TestAccountInfo {
@@ -1047,9 +1043,9 @@ class MultiProfileDownloadNotificationTest
 
     // Logs in to a dummy profile.
     command_line->AppendSwitchASCII(ash::switches::kLoginUser,
-                                    kTestAccounts[DUMMY_ACCOUNT_INDEX].email);
+                                    kTestAccounts[0].email);
     command_line->AppendSwitchASCII(ash::switches::kLoginProfile,
-                                    kTestAccounts[DUMMY_ACCOUNT_INDEX].hash);
+                                    kTestAccounts[0].hash);
     // Don't require policy for our sessions - this is required because
     // this test creates a secondary profile synchronously, so we need to
     // let the policy code know not to expect cached policy.
@@ -1057,24 +1053,24 @@ class MultiProfileDownloadNotificationTest
                                     "false");
   }
 
-  // Logs in to the primary profile.
-  void SetUpOnMainThread() override {
-    const TestAccountInfo& info = kTestAccounts[PRIMARY_ACCOUNT_INDEX];
+  void SetUpLocalStatePrefService(PrefService* local_state) override {
+    InProcessBrowserTest::SetUpLocalStatePrefService(local_state);
 
-    AddUser(info, true);
-    DownloadNotificationTestBase::SetUpOnMainThread();
+    // Register a persisted user.
+    ScopedListPrefUpdate prefs_user_update(
+        local_state, user_manager::prefs::kRegularUsersPref);
+    for (const auto& test_account : kTestAccounts) {
+      prefs_user_update->Append(test_account.email);
+    }
   }
 
-  // Loads all users to the current session and sets up necessary fields.
-  // This is used for preparing all accounts in PRE_ test setup, and for testing
-  // actual login behavior.
-  void AddAllUsers() {
-    for (size_t i = 0; i < std::size(kTestAccounts); ++i) {
-      // The primary account was already set up in SetUpOnMainThread, so skip it
-      // here.
-      if (i == PRIMARY_ACCOUNT_INDEX)
-        continue;
-      AddUser(kTestAccounts[i], i >= SECONDARY_ACCOUNT_INDEX_START);
+  // Logs in to the primary profile.
+  void SetUpOnMainThread() override {
+    DownloadNotificationTestBase::SetUpOnMainThread();
+
+    // Add all users, except the first one, which is already logged in.
+    for (size_t i = 1; i < std::size(kTestAccounts); ++i) {
+      AddUser(kTestAccounts[i]);
     }
   }
 
@@ -1085,12 +1081,11 @@ class MultiProfileDownloadNotificationTest
   }
 
   // Adds a new user for testing to the current session.
-  void AddUser(const TestAccountInfo& info, bool log_in) {
-    if (log_in) {
+  void AddUser(const TestAccountInfo& info) {
     session_manager::SessionManager::Get()->CreateSession(
         AccountId::FromUserEmailGaiaId(info.email, GaiaId(info.gaia_id)),
         info.hash, false);
-    }
+
     user_manager::UserManager::Get()->SaveUserDisplayName(
         AccountId::FromUserEmailGaiaId(info.email, GaiaId(info.gaia_id)),
         base::UTF8ToUTF16(info.display_name));
@@ -1109,15 +1104,8 @@ class MultiProfileDownloadNotificationTest
   std::unique_ptr<NotificationDisplayServiceTester> display_service2_;
 };
 
-IN_PROC_BROWSER_TEST_F(MultiProfileDownloadNotificationTest,
-                       PRE_DownloadMultipleFiles) {
-  AddAllUsers();
-}
-
 IN_PROC_BROWSER_TEST_F(MultiProfileDownloadNotificationTest,
                        DownloadMultipleFiles) {
-  AddAllUsers();
-
   GURL url(SlowDownloadInterceptor::kUnknownSizeUrl);
 
   Profile* profile1 = GetProfileByIndex(1);

chrome/browser/ssl/ssl_browsertest.cc

@@ -224,6 +224,7 @@
 #include "components/policy/core/common/policy_namespace.h"
 #include "components/policy/core/common/policy_service.h"
 #include "components/session_manager/core/session_manager.h"
+#include "components/user_manager/test_helper.h"
 #endif  // BUILDFLAG(IS_CHROMEOS_ASH)
 
 using content::WebContents;
@@ -5655,6 +5656,13 @@ IN_PROC_BROWSER_TEST_F(SSLUITestNoCert, NewCertificateAuthority) {
 // into their NSS databases.
 class SSLUITestCustomCACerts : public SSLUITestNoCert {
  public:
+  static inline constexpr char kPrimaryUserAccount[] = "test1@test.com";
+  static inline constexpr GaiaId::Literal kPrimaryUserGaiaId{"1234567890"};
+  static inline constexpr char kPrimaryUserHash[] = "test1-hash";
+  static inline constexpr char kSecondaryUserAccount[] = "test2@test.com";
+  static inline constexpr GaiaId::Literal kSecondaryUserGaiaId{"9876543210"};
+  static inline constexpr char kSecondaryUserHash[] = "test2-hash";
+
   SSLUITestCustomCACerts() = default;
 
   SSLUITestCustomCACerts(const SSLUITestCustomCACerts&) = delete;
@@ -5668,6 +5676,23 @@ class SSLUITestCustomCACerts : public SSLUITestNoCert {
     // code knows not to expect cached policy for the secondary profile.
     command_line->AppendSwitchASCII(ash::switches::kProfileRequiresPolicy,
                                     "false");
+
+    command_line->AppendSwitchASCII(ash::switches::kLoginUser,
+                                    kPrimaryUserAccount);
+    command_line->AppendSwitchASCII(ash::switches::kLoginProfile,
+                                    kPrimaryUserHash);
+  }
+
+  void SetUpLocalStatePrefService(PrefService* local_state) override {
+    SSLUITestNoCert::SetUpLocalStatePrefService(local_state);
+
+    // Register a persisted user.
+    user_manager::TestHelper::RegisterPersistedUser(
+        *local_state, AccountId::FromUserEmailGaiaId(kPrimaryUserAccount,
+                                                     kPrimaryUserGaiaId));
+    user_manager::TestHelper::RegisterPersistedUser(
+        *local_state, AccountId::FromUserEmailGaiaId(kSecondaryUserAccount,
+                                                     kSecondaryUserGaiaId));
   }
 
   void SetUpOnMainThread() override {
@@ -5677,10 +5702,6 @@ class SSLUITestCustomCACerts : public SSLUITestNoCert {
 
     // Create a second profile.
     {
-      static const char kSecondProfileAccount[] = "profile2@test.com";
-      static const char kSecondProfileGaiaId[] = "9876543210";
-      static const char kSecondProfileHash[] = "testProfile2";
-
       ON_CALL(policy_for_profile_2_, IsInitializationComplete(testing::_))
           .WillByDefault(testing::Return(true));
       ON_CALL(policy_for_profile_2_, IsFirstPolicyLoadComplete(testing::_))
@@ -5691,12 +5712,12 @@ class SSLUITestCustomCACerts : public SSLUITestNoCert {
       base::FilePath user_data_directory;
       base::PathService::Get(chrome::DIR_USER_DATA, &user_data_directory);
       session_manager::SessionManager::Get()->CreateSession(
-          AccountId::FromUserEmailGaiaId(kSecondProfileAccount,
-                                         GaiaId(kSecondProfileGaiaId)),
-          kSecondProfileHash, false);
+          AccountId::FromUserEmailGaiaId(kSecondaryUserAccount,
+                                         kSecondaryUserGaiaId),
+          kSecondaryUserHash, false);
       // Set up the secondary profile.
       base::FilePath profile_dir = user_data_directory.Append(
-          ash::ProfileHelper::GetUserProfileDir(kSecondProfileHash).BaseName());
+          ash::ProfileHelper::GetUserProfileDir(kSecondaryUserHash).BaseName());
       profile_2_ =
           g_browser_process->profile_manager()->GetProfile(profile_dir);
     }

chrome/browser/ui/ash/new_window/chrome_new_window_client_browsertest.cc

@@ -117,8 +117,6 @@ IN_PROC_BROWSER_TEST_F(ChromeNewWindowClientBrowserTest,
 }
 
 IN_PROC_BROWSER_TEST_F(ChromeNewWindowClientBrowserTest, IncognitoDisabled) {
-  CreateAndStartUserSession(
-      AccountId::FromUserEmailGaiaId(kTestUserName1, GaiaId(kTestUser2GaiaId)));
   Profile* profile = ProfileManager::GetActiveUserProfile();
   EXPECT_EQ(1u, chrome::GetTotalBrowserCount());
 

chrome/browser/ui/web_applications/web_app_profile_deletion_browsertest.cc

@@ -40,6 +40,7 @@
 #include "chromeos/ash/components/browser_context_helper/browser_context_helper.h"
 #include "components/account_id/account_id.h"
 #include "components/session_manager/core/session_manager.h"
+#include "components/user_manager/test_helper.h"
 #endif
 
 namespace web_app {
@@ -128,13 +129,19 @@ class WebAppProfileDeletionBrowserTest : public WebAppBrowserTestBase {
   }
 
 #if BUILDFLAG(IS_CHROMEOS)
-  void CreateSession(const AccountId& account_id) {
-    auto* session_manager = session_manager::SessionManager::Get();
-    session_manager->CreateSession(account_id, account_id.GetUserEmail(),
-                                   false);
+  void SetUpLocalStatePrefService(PrefService* local_state) override {
+    WebAppBrowserTestBase::SetUpLocalStatePrefService(local_state);
+
+    // Register a persisted user.
+    user_manager::TestHelper::RegisterPersistedUser(*local_state,
+                                                    test_account_id_);
   }
 
   Profile& StartUserSession(const AccountId& account_id) {
+    auto* session_manager = session_manager::SessionManager::Get();
+    session_manager->CreateSession(account_id, account_id.GetUserEmail(),
+                                   false);
+
     ProfileManager* profile_manager = g_browser_process->profile_manager();
     Profile& profile = profiles::testing::CreateProfileSync(
         profile_manager,
@@ -143,7 +150,6 @@ class WebAppProfileDeletionBrowserTest : public WebAppBrowserTestBase {
                 ->FindUser(account_id)
                 ->username_hash()));
 
-    auto* session_manager = session_manager::SessionManager::Get();
     session_manager->NotifyUserProfileLoaded(account_id);
     session_manager->SessionStarted();
     return profile;
@@ -176,7 +182,6 @@ IN_PROC_BROWSER_TEST_F(WebAppProfileDeletionBrowserTest, OsIntegrationRemoved) {
   /// Create a new profile and install a web app.
   ProfileManager* profile_manager = g_browser_process->profile_manager();
 #if BUILDFLAG(IS_CHROMEOS)
-  CreateSession(test_account_id_);
   Profile& profile_to_delete = StartUserSession(test_account_id_);
 #else
   base::FilePath profile_path_to_delete =
@@ -210,7 +215,6 @@ IN_PROC_BROWSER_TEST_F(WebAppProfileDeletionBrowserTest,
   // Create a new profile.
   ProfileManager* profile_manager = g_browser_process->profile_manager();
 #if BUILDFLAG(IS_CHROMEOS)
-  CreateSession(test_account_id_);
   Profile& profile_to_delete = StartUserSession(test_account_id_);
 #else
   base::FilePath profile_path_to_delete =
@@ -250,7 +254,6 @@ IN_PROC_BROWSER_TEST_F(WebAppProfileDeletionBrowserTest_WebAppPublisher,
   /// Create a new profile and install a web app.
   ProfileManager* profile_manager = g_browser_process->profile_manager();
 #if BUILDFLAG(IS_CHROMEOS)
-  CreateSession(test_account_id_);
   Profile& profile_to_delete = StartUserSession(test_account_id_);
 #else
   base::FilePath profile_path_to_delete =

chrome/browser/ui/webui/ash/settings/pages/a11y/accessibility_handler_browsertest.cc

@@ -11,6 +11,7 @@
 
 #include "ash/constants/ash_features.h"
 #include "ash/constants/ash_pref_names.h"
+#include "ash/constants/ash_switches.h"
 #include "base/containers/adapters.h"
 #include "chrome/browser/ash/accessibility/accessibility_manager.h"
 #include "chrome/browser/ash/input_method/mock_input_method_engine.h"
@@ -24,6 +25,7 @@
 #include "components/language/core/browser/pref_names.h"
 #include "components/language/core/common/locale_util.h"
 #include "components/prefs/pref_service.h"
+#include "components/user_manager/test_helper.h"
 #include "content/public/test/browser_test.h"
 #include "content/public/test/test_web_ui.h"
 #include "google_apis/gaia/gaia_id.h"
@@ -42,7 +44,8 @@ namespace {
 
 // Use a real domain to avoid policy loading problems.
 constexpr char kTestUserName[] = "owner@gmail.com";
-constexpr char kTestUserGaiaId[] = "9876543210";
+constexpr char kTestUserHash[] = "1234567890-hash";
+constexpr GaiaId::Literal kTestUserGaiaId{"9876543210"};
 
 }  // namespace
 
@@ -65,6 +68,20 @@ class AccessibilityHandlerTest : public InProcessBrowserTest {
   void SetUpCommandLine(base::CommandLine* command_line) override {
     scoped_feature_list_.InitWithFeatures(
         {features::kOnDeviceSpeechRecognition}, {});
+
+    // Use a persisted user.
+    command_line->AppendSwitchASCII(ash::switches::kLoginUser, kTestUserName);
+    command_line->AppendSwitchASCII(ash::switches::kLoginProfile,
+                                    kTestUserHash);
+  }
+
+  void SetUpLocalStatePrefService(PrefService* local_state) override {
+    InProcessBrowserTest::SetUpLocalStatePrefService(local_state);
+
+    // Register a persisted user.
+    user_manager::TestHelper::RegisterPersistedUser(
+        *local_state,
+        AccountId::FromUserEmailGaiaId(kTestUserName, kTestUserGaiaId));
   }
 
   void SetUpOnMainThread() override {
@@ -140,25 +157,6 @@ class AccessibilityHandlerTest : public InProcessBrowserTest {
         prefs::kAccessibilityDictationLocale, locale);
   }
 
-  void CreateSession(const AccountId& account_id) {
-    auto* session_manager = session_manager::SessionManager::Get();
-    session_manager->CreateSession(account_id, account_id.GetUserEmail(),
-                                   false);
-  }
-
-  void StartUserSession(const AccountId& account_id) {
-    profiles::testing::CreateProfileSync(
-        g_browser_process->profile_manager(),
-        BrowserContextHelper::Get()->GetBrowserContextPathByUserIdHash(
-            user_manager::UserManager::Get()
-                ->FindUser(account_id)
-                ->username_hash()));
-
-    auto* session_manager = session_manager::SessionManager::Get();
-    session_manager->NotifyUserProfileLoaded(account_id);
-    session_manager->SessionStarted();
-  }
-
   speech::SodaInstaller* soda_installer() {
     return speech::SodaInstaller::GetInstance();
   }
@@ -169,9 +167,6 @@ class AccessibilityHandlerTest : public InProcessBrowserTest {
 
   std::unique_ptr<input_method::MockInputMethodEngine> mock_ime_engine_handler_;
 
-  const AccountId test_account_id_ =
-      AccountId::FromUserEmailGaiaId(kTestUserName, GaiaId(kTestUserGaiaId));
-
  private:
   std::unique_ptr<TestingProfile> profile_;
   std::unique_ptr<TestAccessibilityHandler> handler_;
@@ -344,8 +339,6 @@ IN_PROC_BROWSER_TEST_F(AccessibilityHandlerTest,
 }
 
 IN_PROC_BROWSER_TEST_F(AccessibilityHandlerTest, GetStartupSoundEnabled) {
-  CreateSession(test_account_id_);
-  StartUserSession(test_account_id_);
   AccessibilityManager::Get()->SetStartupSoundEnabled(true);
 
   size_t call_data_count_before_call = web_ui()->call_data().size();

components/user_manager/BUILD.gn

@@ -90,6 +90,8 @@ if (is_chromeos) {
       "fake_user_manager.h",
       "fake_user_manager_delegate.cc",
       "fake_user_manager_delegate.h",
+      "test_helper.cc",
+      "test_helper.h",
     ]
 
     public_deps = [
@@ -99,7 +101,10 @@ if (is_chromeos) {
       "//components/account_id",
     ]
 
-    deps = [ "//chromeos/ash/components/settings" ]
+    deps = [
+      "//chromeos/ash/components/settings",
+      "//components/prefs",
+    ]
   }
 
   source_set("unit_tests") {

components/user_manager/test_helper.cc

@@ -0,0 +1,27 @@
+// Copyright 2025 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/user_manager/test_helper.h"
+
+#include "components/account_id/account_id.h"
+#include "components/prefs/scoped_user_pref_update.h"
+#include "components/user_manager/known_user.h"
+#include "components/user_manager/user_manager_pref_names.h"
+
+namespace user_manager {
+
+// static
+void TestHelper::RegisterPersistedUser(PrefService& local_state,
+                                       const AccountId& account_id) {
+  {
+    ScopedListPrefUpdate update(&local_state, prefs::kRegularUsersPref);
+    update->Append(account_id.GetUserEmail());
+  }
+  {
+    KnownUser known_user(&local_state);
+    known_user.UpdateId(account_id);
+  }
+}
+
+}  // namespace user_manager

components/user_manager/test_helper.h

@@ -0,0 +1,32 @@
+// Copyright 2025 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_USER_MANAGER_TEST_HELPER_H_
+#define COMPONENTS_USER_MANAGER_TEST_HELPER_H_
+
+class AccountId;
+class PrefService;
+
+namespace user_manager {
+
+// Utilities to set up UserManager related environment.
+class TestHelper {
+ public:
+  // Records the `account_id` as a persisted user to the given `local_state`.
+  // `local_state` must be properly set up, specifically it needs UserManager
+  // related registration.
+  // In most cases, this registration needs to be done before UserManager
+  // is created. Specifically, for browser_tests, SetUpLocalStatePrefService()
+  // is a recommended function to call this.
+  static void RegisterPersistedUser(PrefService& local_state,
+                                    const AccountId& account_id);
+
+ private:
+  // Currently, this has only static methods.
+  TestHelper() = delete;
+};
+
+}  // namespace user_manager
+
+#endif  // COMPONENTS_USER_MANAGER_TEST_HELPER_H_

components/user_manager/user_manager_impl.cc

@@ -275,9 +275,13 @@ void UserManagerImpl::UserLoggedIn(const AccountId& account_id,
 
   User* user = FindUserInListAndModify(account_id);
 
-  const UserType user_type =
-      CalculateUserType(account_id, user, browser_restart, is_child);
-  if (active_user_ && user) {
+  if (!logged_in_users_.empty()) {
+    // Handle multi sign-in case. For multi-sign in, there already should be
+    // active_user_ set, and the user to be logged in should be found
+    // in the persistent user list.
+    CHECK(active_user_);
+    CHECK(user);
+
     user->set_is_logged_in(true);
     user->set_username_hash(username_hash);
     logged_in_users_.push_back(user);
@@ -300,7 +304,12 @@ void UserManagerImpl::UserLoggedIn(const AccountId& account_id,
     return;
   }
 
+  // There are no logged in users. `active_user_` should not be set.
+  CHECK(!active_user_);
+
   // Ensure User is there.
+  const UserType user_type =
+      CalculateUserType(account_id, user, browser_restart, is_child);
   switch (user_type) {
     case UserType::kRegular:
     case UserType::kChild: