diff --git a/tests/phpunit/tests/admin/includes/misc/heartbeatAutosave.php b/tests/phpunit/tests/admin/includes/misc/heartbeatAutosave.php
new file mode 100644
index 0000000000000..08ec76af470b8
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/misc/heartbeatAutosave.php
@@ -0,0 +1,106 @@
+<?php
+/**
+ * Test heartbeat_autosave().
+ *
+ * @group admin
+ * @group heartbeat
+ *
+ * @covers ::heartbeat_autosave
+ */
+class Tests_Admin_Includes_Misc_HeartbeatAutosave extends WP_UnitTestCase {
+
+	/**
+	 * Tests that heartbeat_autosave() correctly handles missing autosave data.
+	 *
+	 * @ticket 65201
+	 */
+	public function test_heartbeat_autosave_no_data() {
+		$response = array( 'existing' => 'data' );
+		$data     = array();
+
+		$result = heartbeat_autosave( $response, $data );
+
+		$this->assertSame( $response, $result, 'The response should remain unchanged when no autosave data is provided.' );
+	}
+
+	/**
+	 * Tests that heartbeat_autosave() correctly handles successful autosave.
+	 *
+	 * @ticket 65201
+	 */
+	public function test_heartbeat_autosave_success() {
+		$post_id = self::factory()->post->create();
+		$user_id = self::factory()->user->create( array( 'role' => 'editor' ) );
+		wp_set_current_user( $user_id );
+
+		$response = array();
+		$data     = array(
+			'wp_autosave' => array(
+				'post_id'      => $post_id,
+				'post_type'    => 'post',
+				'_wpnonce'     => wp_create_nonce( 'update-post_' . $post_id ),
+				'post_content' => 'Autosaved content',
+			),
+		);
+
+		$result = heartbeat_autosave( $response, $data );
+
+		$this->assertArrayHasKey( 'wp_autosave', $result );
+		$this->assertTrue( $result['wp_autosave']['success'] );
+		$this->assertStringContainsString( 'Draft saved at', $result['wp_autosave']['message'] );
+	}
+
+	/**
+	 * Tests that heartbeat_autosave() correctly handles autosave errors.
+	 *
+	 * @ticket 65201
+	 */
+	public function test_heartbeat_autosave_error() {
+		$post_id = self::factory()->post->create();
+		$user_id = self::factory()->user->create( array( 'role' => 'editor' ) );
+		wp_set_current_user( $user_id );
+
+		$response = array();
+		$data     = array(
+			'wp_autosave' => array(
+				'post_id'  => $post_id,
+				'_wpnonce' => 'invalid-nonce',
+			),
+		);
+
+		$result = heartbeat_autosave( $response, $data );
+
+		$this->assertArrayHasKey( 'wp_autosave', $result );
+		$this->assertFalse( $result['wp_autosave']['success'] );
+		$this->assertSame( 'Error while saving.', $result['wp_autosave']['message'] );
+	}
+
+	/**
+	 * Tests that heartbeat_autosave() handles empty return from wp_autosave().
+	 *
+	 * @ticket 65201
+	 */
+	public function test_heartbeat_autosave_empty_result() {
+		$post_id = self::factory()->post->create();
+		$user_id = self::factory()->user->create( array( 'role' => 'editor' ) );
+		wp_set_current_user( $user_id );
+
+		$response = array();
+		$data     = array(
+			'wp_autosave' => array(
+				'post_id'   => $post_id,
+				'post_type' => 'post',
+				'_wpnonce'  => wp_create_nonce( 'update-post_' . $post_id ),
+			),
+		);
+
+		// Trigger an empty return by making edit_post return 0.
+		add_filter( 'wp_insert_post_empty_content', '__return_true' );
+
+		$result = heartbeat_autosave( $response, $data );
+
+		$this->assertArrayHasKey( 'wp_autosave', $result );
+		$this->assertFalse( $result['wp_autosave']['success'] );
+		$this->assertSame( 'Content, title, and excerpt are empty.', $result['wp_autosave']['message'] );
+	}
+}