samples: bluetooth: fast_pair: locator_tag: doc: update testing section

Updated the testing section in the Readme file of the Fast Pair Locator
tag sample. The new content describes the procedure to test the firmware
update notification feature.

Ref: NCSDK-32027

Signed-off-by: Kamil Piszczek <[email protected]>

Author: kapi-no

doc/nrf/images/bt_fast_pair_locator_tag_android_fw_update_notification.png

@@ -704,6 +704,12 @@ Testing
 
       #. Initiate the connection and trigger the Fast Pair procedure by tapping the :guilabel:`Connect` button.
          After the procedure is complete, you will see a pop-up with the Acceptable Use Policy for the `Find My Device app`_.
+
+         .. note::
+            If you use the default debug device model and you have the `nRF Connect Device Manager`_ application installed on your test Android device, you may get the Android notification from this mobile application about the new firmware update.
+            You can ignore this notification, as it is not related to the Fast Pair provisioning process.
+            To test the notification feature, follow the :ref:`fast_pair_locator_tag_testing_fw_update_notifications` test section.
+
       #. If you want to start the FMDN provisioning, accept the Acceptable Use Policy by tapping the :guilabel:`Agree and continue` button.
 
          .. figure:: /images/bt_fast_pair_locator_tag_acceptable_use_policy.png
@@ -768,6 +774,12 @@ Testing
 
       #. Initiate the connection and trigger the Fast Pair procedure by tapping the :guilabel:`Connect` button.
          After the procedure is complete, you will see a pop-up with the Acceptable Use Policy for the `Find My Device app`_.
+
+         .. note::
+            If you use the default debug device model and you have the `nRF Connect Device Manager`_ application installed on your test Android device, you may get the Android notification from this mobile application about the new firmware update.
+            You can ignore this notification, as it is not related to the Fast Pair provisioning process.
+            To test the notification feature, follow the :ref:`fast_pair_locator_tag_testing_fw_update_notifications` test section.
+
       #. If you want to start the FMDN provisioning, accept the Acceptable Use Policy by tapping the :guilabel:`Agree and continue` button.
 
          .. figure:: /images/bt_fast_pair_locator_tag_acceptable_use_policy.png
@@ -816,12 +828,17 @@ Testing
       #. Observe that the Android does not display a notification about the detected Fast Pair Provider, as the locator tag device disables advertising after the unprovisioning operation.
       #. Press **Button 0** to request turning on the Fast Pair advertising in discoverable mode and to restart the FMDN provisioning process.
 
+.. _fast_pair_locator_tag_testing_clock_sync:
 
 Clock synchronization
 ---------------------
 
 Testing steps for the clock synchronization feature require a second Android device.
 The device must be registered to a **different** Google account from the first Android device.
+Testing steps also require the `nRF Connect for Mobile`_ application on your second Android device.
+
+.. note::
+   You can execute these testing steps in combination with the :ref:`fast_pair_locator_tag_testing_fw_update_notifications` testing steps, as both test variants require you to wait for more than 24 hours.
 
 To test this feature, complete the following steps:
 
@@ -1028,9 +1045,13 @@ To test this feature, complete the following steps:
       #. Turn on your Android device.
       #. Observe that after up to few hours the **LED 1** goes off, which means that the motion detector has been deactivated, because the device is no longer in the Unwanted Tracking Protection mode.
 
+.. _fast_pair_locator_tag_testing_dfu:
+
 Performing the DFU procedure
 ----------------------------
 
+Testing steps for the DFU feature require the `nRF Connect Device Manager`_ application on your test Android device.
+
 To perform the DFU procedure, complete the following steps:
 
 .. tabs::
@@ -1069,6 +1090,101 @@ To perform the DFU procedure, complete the following steps:
 
          .. include:: /includes/suit_fota_update_nrfcdm_test_steps.txt
 
+.. _fast_pair_locator_tag_testing_fw_update_notifications:
+
+Android notifications about firmware updates
+--------------------------------------------
+
+Testing steps for the firmware update notification feature require the `nRF Connect Device Manager`_ application on your test Android device.
+
+.. note::
+   The support for the Android notifications about the firmware updates in the context of the FMDN extension is a new feature.
+   Before you start the testing, ensure that versions for the following applications and services are equal to or greater than the specified minimum versions:
+
+   * `Google Play Services`_ - ``v25.12.33``
+   * `nRF Connect Device Manager`_ - ``v2.5.0``
+
+.. note::
+   You can execute these testing steps in combination with the :ref:`fast_pair_locator_tag_testing_clock_sync` testing steps, as both test variants require you to wait for more than 24 hours.
+
+To test this feature, complete the following steps:
+
+.. tabs::
+
+   .. group-tab:: nRF52 and nRF53 DKs
+
+      1. Go to the :ref:`fast_pair_locator_tag_testing` section and follow the instructions on performing the FMDN provisioning operation.
+      #. Observe that **LED 3** is lit, which indicates that the device is provisioned as an FMDN beacon.
+      #. Power off the development kit and wait for 24 hours.
+      #. Power off your test Android device.
+      #. Power on the development kit.
+      #. |connect_terminal_specific|
+      #. Power on your test Android device and unlock it after the smartphone screen is turned on.
+      #. Wait for the Android device to connect to the development kit, read the local firmware version, and disconnect.
+      #. Observe that you get the Android notification about the new firmware update on your test Android device.
+
+         .. figure:: /images/bt_fast_pair_locator_tag_android_fw_update_notification.png
+            :scale: 80 %
+            :alt: Firmware update notification in the Android notification center
+
+      #. Upgrade the sample firmware to the latest version:
+
+         a. Set the application firmware version to ``v99.99.99`` by modifying the following files:
+
+            * The :file:`VERSION` file.
+            * The :file:`configuration/prj.conf` file (the :kconfig:option:`CONFIG_BT_FAST_PAIR_FMDN_DULT_FIRMWARE_VERSION_MAJOR`, :kconfig:option:`CONFIG_BT_FAST_PAIR_FMDN_DULT_FIRMWARE_VERSION_MINOR`, and :kconfig:option:`CONFIG_BT_FAST_PAIR_FMDN_DULT_FIRMWARE_VERSION_REVISION` Kconfig option group).
+
+            The new firmware version should match the version specified in the **Firmware Version** field from the :ref:`fast_pair_locator_tag_google_device_model` section.
+
+         #. Rebuild the sample application to generate the DFU package.
+         #. Follow the instructions from the :ref:`fast_pair_locator_tag_testing_dfu` section to perform the DFU procedure.
+
+      #. Validate the new firmware version is correct by reading the application boot banner.
+      #. Power off the development kit and wait again for 24 hours.
+      #. Power off your test Android device.
+      #. Power on the development kit.
+      #. |connect_terminal_specific|
+      #. Power on your test Android device and unlock it after the smartphone screen is turned on.
+      #. Wait for the Android device to connect to the development kit, read the local firmware version, and disconnect.
+      #. Observe that you no longer get the Android notification about the new firmware update on your test Android device.
+
+   .. group-tab:: nRF54 DKs
+
+      1. Go to the :ref:`fast_pair_locator_tag_testing` section and follow the instructions on performing the FMDN provisioning operation.
+      #. Observe that **LED 2** is lit, which indicates that the device is provisioned as an FMDN beacon.
+      #. Power off the development kit and wait for 24 hours.
+      #. Power off your test Android device.
+      #. Power on the development kit.
+      #. |connect_terminal_specific|
+      #. Power on your test Android device and unlock it after the smartphone screen is turned on.
+      #. Wait for the Android device to connect to the development kit, read the local firmware version, and disconnect.
+      #. Observe that you get the Android notification about the new firmware update on your test Android device.
+
+         .. figure:: /images/bt_fast_pair_locator_tag_android_fw_update_notification.png
+            :scale: 80 %
+            :alt: Firmware update notification in the Android notification center
+
+      #. Upgrade the sample firmware to the latest version:
+
+         a. Set the application firmware version to ``v99.99.99`` by modifying the following files:
+
+            * The :file:`VERSION` file.
+            * The :file:`configuration/prj.conf` file (the :kconfig:option:`CONFIG_BT_FAST_PAIR_FMDN_DULT_FIRMWARE_VERSION_MAJOR`, :kconfig:option:`CONFIG_BT_FAST_PAIR_FMDN_DULT_FIRMWARE_VERSION_MINOR`, and :kconfig:option:`CONFIG_BT_FAST_PAIR_FMDN_DULT_FIRMWARE_VERSION_REVISION` Kconfig option group).
+
+            The new firmware version should match the version specified in the **Firmware Version** field from the :ref:`fast_pair_locator_tag_google_device_model` section.
+
+         #. Rebuild the sample application to generate the DFU package.
+         #. Follow the instructions from the :ref:`fast_pair_locator_tag_testing_dfu` section to perform the DFU procedure.
+
+      #. Validate the new firmware version is correct by reading the application boot banner.
+      #. Power off the development kit and wait again for 24 hours.
+      #. Power off your test Android device.
+      #. Power on the development kit.
+      #. |connect_terminal_specific|
+      #. Power on your test Android device and unlock it after the smartphone screen is turned on.
+      #. Wait for the Android device to connect to the development kit, read the local firmware version, and disconnect.
+      #. Observe that you no longer get the Android notification about the new firmware update on your test Android device.
+
 Disabling the locator tag
 -------------------------