diff --git a/tests/phpunit/tests/functions/wpFindHierarchyLoop.php b/tests/phpunit/tests/functions/wpFindHierarchyLoop.php
new file mode 100644
index 0000000000000..12621844b4609
--- /dev/null
+++ b/tests/phpunit/tests/functions/wpFindHierarchyLoop.php
@@ -0,0 +1,46 @@
+<?php
+
+/**
+ * Tests for the wp_find_hierarchy_loop function.
+ *
+ * @group Functions.php
+ *
+ * @covers ::wp_find_hierarchy_loop
+ */
+class Tests_Functions_wpFindHierarchyLoop extends WP_UnitTestCase {
+
+	/**
+	 * @ticket 59901
+	 */
+	public function test_wp_find_hierarchy_loop() {
+		$result   = wp_find_hierarchy_loop(
+			static function ( $id ) {
+				return 1;
+			},
+			1,
+			2
+		);
+		$expected = array(
+			1 => true,
+			2 => true,
+		);
+		$this->assertSame( $expected, $result );
+	}
+
+	/**
+	 * @ticket 59901
+	 */
+	public function test_wp_find_hierarchy_loop_null_parent() {
+		$result   = wp_find_hierarchy_loop(
+			static function ( $id ) {
+				return 1;
+			},
+			1,
+			null
+		);
+		$expected = array(
+			1 => true,
+		);
+		$this->assertSame( $expected, $result );
+	}
+}