diff --git a/tools/chatgui/CMakeLists.txt b/tools/chatgui/CMakeLists.txt
index 649593e9..f421dd70 100644
--- a/tools/chatgui/CMakeLists.txt
+++ b/tools/chatgui/CMakeLists.txt
@@ -308,7 +308,14 @@ enable_testing()
 
 add_executable(test_message_notification tests/test_message_notification.cpp)
 target_link_libraries(test_message_notification PRIVATE chatgui_notifications ${QT_TEST_LIB} pthread ${CMAKE_DL_LIBS})
-add_test(NAME test_message_notification COMMAND test_message_notification)
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    find_program(NOTIFICATION_DBUS_RUN_SESSION dbus-run-session REQUIRED)
+    target_compile_definitions(test_message_notification PRIVATE UTUN_TEST_ACTIVITY_DBUS)
+    target_link_libraries(test_message_notification PRIVATE ${QT_DBUS})
+    add_test(NAME test_message_notification COMMAND ${NOTIFICATION_DBUS_RUN_SESSION} -- $<TARGET_FILE:test_message_notification>)
+else()
+    add_test(NAME test_message_notification COMMAND test_message_notification)
+endif()
 set_tests_properties(test_message_notification PROPERTIES ENVIRONMENT "QT_QPA_PLATFORM=offscreen" TIMEOUT 60)
 
 add_executable(test_file_drop tests/test_file_drop.cpp src/inputbar.cpp src/audiorecorder.cpp src/audio_device.cpp src/sound_manager.cpp
diff --git a/tools/chatgui/tests/test_message_notification.cpp b/tools/chatgui/tests/test_message_notification.cpp
new file mode 100644
index 00000000..3ee637c9
--- /dev/null
+++ b/tools/chatgui/tests/test_message_notification.cpp
@@ -0,0 +1,178 @@
+/* Проверяем время жизни уведомления и первую активность без ввода в настоящую desktop-сессию. */
+#include "../src/message_notification.h"
+#include "../src/user_activity_monitor.h"
+#include "../../../lib/debug_config.h"
+
+#include <QtTest>
+#include <QLineEdit>
+#include <QPushButton>
+#include <QScreen>
+#include <QMouseEvent>
+
+#ifdef UTUN_TEST_ACTIVITY_DBUS
+#include <QDBusConnection>
+#include <QDBusContext>
+#include <QDBusMessage>
+#endif
+
+class FakeSystemActivity : public UserActivityMonitor {
+public:
+    FakeSystemActivity() { clock.start(); }
+    QElapsedTimer clock;
+    qint64 lastInput = -5000;
+    bool available = true;
+protected:
+    qint64 systemIdleTime() override { return available ? clock.elapsed() - lastInput : -1; }
+};
+
+#ifdef UTUN_TEST_ACTIVITY_DBUS
+class FakeGnomeIdle : public QObject, protected QDBusContext {
+    Q_OBJECT
+    Q_CLASSINFO("D-Bus Interface", "org.gnome.Mutter.IdleMonitor")
+public:
+    FakeGnomeIdle() { clock.start(); }
+    QElapsedTimer clock;
+    qint64 lastInput = -5000;
+    int delayMs = 0;
+    int requests = 0;
+public slots:
+    qulonglong GetIdletime() {
+        ++requests;
+        const qulonglong idle = clock.elapsed() - lastInput;
+        if (delayMs) {
+            const QDBusMessage reply = message().createReply(QVariant::fromValue(idle));
+            setDelayedReply(true);
+            QTimer::singleShot(delayMs, this, [reply] { QDBusConnection::sessionBus().send(reply); });
+        }
+        return idle;
+    }
+};
+#endif
+
+class MessageNotificationTest : public QObject {
+    Q_OBJECT
+private slots:
+    void initTestCase() {
+        debug_config_init();
+        debug_set_level(DEBUG_LEVEL_DEBUG);
+        qunsetenv("XDG_SESSION_TYPE");
+    }
+
+    void firstSystemActivityAndCancellation() {
+        FakeSystemActivity activity;
+        QSignalSpy spy(&activity, &UserActivityMonitor::activity);
+        activity.start();
+        QTest::qWait(600);
+        QCOMPARE(spy.size(), 0); // Старый ввод до начала наблюдения не считается активностью.
+        activity.lastInput = activity.clock.elapsed();
+        QTRY_COMPARE_WITH_TIMEOUT(spy.size(), 1, 700);
+        QTest::qWait(300);
+        QCOMPARE(spy.size(), 1);
+        activity.start();
+        activity.stop();
+        activity.lastInput = activity.clock.elapsed();
+        QTest::qWait(400);
+        QCOMPARE(spy.size(), 1);
+        activity.start();
+        QTest::qWait(20);
+        activity.lastInput = activity.clock.elapsed();
+        QTRY_COMPARE_WITH_TIMEOUT(spy.size(), 2, 700);
+    }
+
+    void localFallbackDoesNotConsumeInput() {
+        FakeSystemActivity activity;
+        activity.available = false;
+        QSignalSpy spy(&activity, &UserActivityMonitor::activity);
+        QLineEdit input;
+        input.show();
+        activity.start();
+        QTest::keyClick(&input, Qt::Key_A);
+        QTest::keyClick(&input, Qt::Key_B);
+        QCOMPARE(input.text(), QString("ab"));
+        QCOMPARE(spy.size(), 1);
+    }
+
+    void waitsForActivityThenExpiresWithoutExtension() {
+        QWidget hiddenParent;
+        QLineEdit otherWindow;
+        otherWindow.show();
+        QApplication::setActiveWindow(&otherWindow);
+        MessageNotification notification(&hiddenParent);
+        notification.showMessage("42", "Alice", "Test channel", {});
+        QVERIFY(notification.isVisible());
+        QCOMPARE(QApplication::activeWindow(), &otherWindow);
+        QTest::qWait(10200);
+        QVERIFY(notification.isVisible()); // Без активности автоматического таймера нет.
+        QElapsedTimer elapsed;
+        elapsed.start();
+        QTest::keyClick(&otherWindow, Qt::Key_A);
+        QTest::qWait(5500);
+        QVERIFY(notification.isVisible());
+        QTest::keyClick(&otherWindow, Qt::Key_B);
+        QTRY_VERIFY_WITH_TIMEOUT(!notification.isVisible(), 6000);
+        QVERIFY(elapsed.elapsed() >= 10000);
+        QVERIFY(elapsed.elapsed() < 12000);
+        QCOMPARE(otherWindow.text(), QString("ab"));
+    }
+
+    void replacementCancelsOldCountdownAndOpensLatestChat() {
+        QLineEdit otherWindow;
+        otherWindow.show();
+        MessageNotification notification;
+        QSignalSpy activated(&notification, &MessageNotification::activated);
+        notification.showMessage("42", "Alice", "First channel", {});
+        QTest::keyClick(&otherWindow, Qt::Key_A);
+        QTest::qWait(100);
+        notification.showMessage("dm:7", "Bob", "Direct messages", QRect(-10, -10, 20, 20));
+        QTest::qWait(10200);
+        QVERIFY(notification.isVisible()); // Прежний таймер не закрывает новое уведомление.
+        const QRect area = notification.screen()->availableGeometry();
+        QVERIFY(area.contains(notification.geometry()));
+        QTest::mouseClick(&notification, Qt::LeftButton, Qt::NoModifier, QPoint(30, notification.height() - 15));
+        QVERIFY(!notification.isVisible());
+        QCOMPARE(activated.size(), 1);
+        QCOMPARE(activated[0][0].toString(), QString("dm:7"));
+        notification.showMessage("43", "Charlie", "Third channel", {});
+        auto* closeButton = notification.findChild<QPushButton*>("notificationCloseButton");
+        QVERIFY(closeButton);
+        QTest::mouseClick(closeButton, Qt::LeftButton);
+        QVERIFY(!notification.isVisible());
+        QCOMPARE(activated.size(), 1);
+    }
+
+#ifdef UTUN_TEST_ACTIVITY_DBUS
+    void gnomeIdleAndStaleReplies() {
+        auto bus = QDBusConnection::sessionBus();
+        QVERIFY(bus.registerService("org.gnome.Mutter.IdleMonitor"));
+        FakeGnomeIdle idle;
+        QVERIFY(bus.registerObject("/org/gnome/Mutter/IdleMonitor/Core", &idle, QDBusConnection::ExportAllSlots));
+        qputenv("XDG_SESSION_TYPE", "wayland");
+        UserActivityMonitor activity;
+        QSignalSpy spy(&activity, &UserActivityMonitor::activity);
+        activity.start();
+        QTRY_VERIFY_WITH_TIMEOUT(idle.requests >= 2, 1000);
+        QCOMPARE(spy.size(), 0);
+        idle.lastInput = idle.clock.elapsed();
+        QTRY_COMPARE_WITH_TIMEOUT(spy.size(), 1, 1000);
+
+        idle.delayMs = 300;
+        activity.start();
+        QTest::qWait(20);
+        idle.lastInput = idle.clock.elapsed();
+        const int before = idle.requests;
+        QTRY_VERIFY_WITH_TIMEOUT(idle.requests > before, 1000);
+        activity.stop();
+        idle.lastInput = idle.clock.elapsed() - 5000;
+        activity.start();
+        QTest::qWait(800);
+        QCOMPARE(spy.size(), 1); // Ответ об активности прежнего наблюдения должен быть отброшен.
+        activity.stop();
+        qunsetenv("XDG_SESSION_TYPE");
+        bus.unregisterObject("/org/gnome/Mutter/IdleMonitor/Core");
+        bus.unregisterService("org.gnome.Mutter.IdleMonitor");
+    }
+#endif
+};
+
+QTEST_MAIN(MessageNotificationTest)
+#include "test_message_notification.moc"