diff --git a/tests/legacy/unit-tests/admin/notes/class-wc-tests-notes-run-db-update.php b/tests/legacy/unit-tests/admin/notes/class-wc-tests-notes-run-db-update.php
new file mode 100644
index 00000000000..fe9ba9e72f4
--- /dev/null
+++ b/tests/legacy/unit-tests/admin/notes/class-wc-tests-notes-run-db-update.php
@@ -0,0 +1,191 @@
+<?php
+/**
+ * Class WC_Notes_Run_Db_Update file.
+ *
+ * @package WooCommerce\Tests\Admin\Notes
+ */
+
+use \Automattic\WooCommerce\Admin\Notes\WC_Admin_Note;
+
+/**
+ * Tests for the WC_Notes_Run_Db_Update class.
+ */
+class WC_Tests_Notes_Run_Db_Update extends WC_Unit_Test_Case {
+
+	/**
+	 * Load the necessary files, as they're not automatically loaded by WooCommerce.
+	 *
+	 */
+	public static function setUpBeforeClass() {
+		include_once WC_Unit_Tests_Bootstrap::instance()->plugin_dir . '/includes/admin/notes/class-wc-notes-run-db-update.php';
+
+	}
+
+	/**
+	 * Clean up before each test.
+	 */
+	public function setUp() {
+		self::remove_db_update_notes();
+	}
+
+	/**
+	 * Returns a list of note ids with name 'wc-update-db-reminder' from the database.
+	 *
+	 * @return array(int) List of note ids with name 'wc-update-db-reminder'.
+	 */
+	private static function get_db_update_notes() {
+		$data_store = \WC_Data_Store::load( 'admin-note' );
+		$note_ids   = $data_store->get_notes_with_name( WC_Notes_Run_Db_Update::NOTE_NAME );
+		return $note_ids;
+	}
+
+	/**
+	 * Removes all the notes with name 'wc-update-db-reminder' from the database.
+	 */
+	private static function remove_db_update_notes() {
+		$data_store = \WC_Data_Store::load( 'admin-note' );
+		$note_ids   = $data_store->get_notes_with_name( WC_Notes_Run_Db_Update::NOTE_NAME );
+		foreach ( $note_ids as $note_id ) {
+			$note = new WC_Admin_Note( $note_id );
+			$data_store->delete( $note );
+		}
+	}
+
+	/**
+	 * Creates a sample note with name 'wc-update-db-reminder'.
+	 *
+	 * @return int Newly create note's id.
+	 */
+	private static function create_db_update_note() {
+		$update_url = html_entity_decode(
+			wp_nonce_url(
+				add_query_arg( 'do_update_woocommerce', 'true', admin_url( 'admin.php?page=wc-settings' ) ),
+				'wc_db_update',
+				'wc_db_update_nonce'
+			)
+		);
+
+		$note_actions = array(
+			array(
+				'name'    => 'update-db_run',
+				'label'   => __( 'Update WooCommerce Database', 'woocommerce' ),
+				'url'     => $update_url,
+				'status'  => 'unactioned',
+				'primary' => true,
+			),
+			array(
+				'name'    => 'update-db_learn-more',
+				'label'   => __( 'Learn more about updates', 'woocommerce' ),
+				'url'     => 'https://docs.woocommerce.com/document/how-to-update-woocommerce/',
+				'status'  => 'unactioned',
+				'primary' => false,
+			),
+		);
+
+		$note = new WC_Admin_Note();
+
+		$note->set_title( 'WooCommerce database update required' );
+		$note->set_content( 'To keep things running smoothly, we have to update your database to the newest version.' );
+		$note->set_type( WC_Admin_Note::E_WC_ADMIN_NOTE_UPDATE );
+		$note->set_icon( 'info' );
+		$note->set_name( WC_Notes_Run_Db_Update::NOTE_NAME );
+		$note->set_content_data( (object) array() );
+		$note->set_source( 'woocommerce-core' );
+		$note->set_status( WC_Admin_Note::E_WC_ADMIN_NOTE_UNACTIONED );
+
+		// Set new actions.
+		$note->clear_actions();
+		foreach ( $note_actions as $note_action ) {
+			$note->add_action( ...array_values( $note_action ) );
+		}
+
+		return $note->save();
+	}
+
+	/**
+	 * No note should be created/exist if db version is equal to WC code version.
+	 */
+	public function test_noop_db_update_note() {
+		update_option( 'woocommerce_db_version', WC()->version );
+
+		// No notes initially.
+		$this->assertEquals( 0, count( self::get_db_update_notes() ), 'There should be no db update notes initially.' );
+
+		WC_Notes_Run_Db_Update::show_reminder();
+
+		// No notice should be created.
+		$this->assertEquals( 0, count( self::get_db_update_notes() ), 'There should be no db update notes created if db is up to date.' );
+	}
+
+
+	/**
+	 * Note should be created if there is none and WC is updated.
+	 */
+	public function test_create_db_update_note() {
+		// No notes initially.
+		$this->assertEquals( 0, count( self::get_db_update_notes() ), 'There should be no db update notes initially.' );
+
+		// Make it appear as if db version is lower than WC version, i.e. db update is required.
+		update_option( 'woocommerce_db_version', '3.9.0' );
+
+		WC_Notes_Run_Db_Update::show_reminder();
+
+		// A notice should be created.
+		$this->assertEquals( 1, count( self::get_db_update_notes() ), 'A db update note should be created if db is NOT up to date.' );
+
+		// Update the db option back.
+		update_option( 'woocommerce_db_version', WC()->version );
+	}
+
+	/**
+	 * Note should be created if there is none and WC is updated.
+	 */
+	public function test_clean_up_multiple_db_update_notes() {
+		// No notes initially.
+		$this->assertEquals( 0, count( self::get_db_update_notes() ), 'There should be no db update notes initially.' );
+
+		$note_1 = self::create_db_update_note();
+		$note_2 = self::create_db_update_note();
+
+		$this->assertEquals( 2, count( self::get_db_update_notes() ), 'There should be 2 db update notes after I created 2.' );
+
+		WC_Notes_Run_Db_Update::show_reminder();
+
+		// Only one notice should remain, in case 2 were created under some weird circumstances.
+		$this->assertEquals( 1, count( self::get_db_update_notes() ), 'A db update note should be created if db is NOT up to date.' );
+
+	}
+
+	/**
+	 * Test switch from db update needed to thanks note.
+	 */
+	public function test_db_update_note_to_thanks_note() {
+		// No notes initially.
+		$this->assertEquals( 0, count( self::get_db_update_notes() ), 'There should be no db update notes initially.' );
+
+		// Make it appear as if db version is lower than WC version, i.e. db update is required.
+		update_option( 'woocommerce_db_version', '3.9.0' );
+
+		// Magic 1: nothing to update-db note.
+		WC_Notes_Run_Db_Update::show_reminder();
+
+		$note_ids = self::get_db_update_notes();
+		// An 'update required' notice should be created.
+		$this->assertEquals( 1, count( $note_ids ), 'A db update note should be created if db is NOT up to date.' );
+
+		$note = new WC_Admin_Note( $note_ids[0] );
+		$actions = $note->get_actions();
+		$this->assertEquals( 'update-db_run', $actions[0]->name, 'A db update note to update the database should be displayed now.' );
+
+		// Simulate database update has been performed.
+		update_option( 'woocommerce_db_version', WC()->version );
+
+		// Magic 2: update-db note to thank you note.
+		WC_Notes_Run_Db_Update::show_reminder();
+
+		$note = new WC_Admin_Note( $note_ids[0] );
+		$actions = $note->get_actions();
+		$this->assertEquals( 'update-db_done', $actions[0]->name, 'A db update note--Thanks for the update--should be displayed now.' );
+	}
+
+}