diff --git a/testing/web-platform/tests/dom/nodes/moveBefore/tentative/Node-moveBefore.html b/testing/web-platform/tests/dom/nodes/moveBefore/tentative/Node-moveBefore.html
index cdb503a6d3ca..180aa7aeca7a 100644
--- a/testing/web-platform/tests/dom/nodes/moveBefore/tentative/Node-moveBefore.html
+++ b/testing/web-platform/tests/dom/nodes/moveBefore/tentative/Node-moveBefore.html
@@ -2175,12 +2175,104 @@
 .
 moveBefore
 (
+c
+b
+)
+undefined
+"
+moveBefore
+(
+)
+returns
+undefined
+"
+)
+;
+assert_array_equals
+(
+a
+.
+childNodes
+[
+c
 b
+]
+)
+;
+}
+"
+moveBefore
+(
+)
+returns
+undefined
+"
+)
+;
+test
+(
+(
+)
+=
+>
+{
+const
+a
+=
+document
+.
+body
+.
+appendChild
+(
+document
+.
+createElement
+(
+"
+div
+"
+)
+)
+;
+const
 b
+=
+document
+.
+createElement
+(
+"
+div
+"
+)
+;
+const
+c
+=
+document
+.
+createElement
+(
+"
+div
+"
 )
+;
+a
+.
+append
+(
 b
 )
 ;
+a
+.
+append
+(
+c
+)
+;
 assert_array_equals
 (
 a
@@ -2192,15 +2284,30 @@
 ]
 )
 ;
-assert_equals
-(
 a
 .
 moveBefore
 (
+b
+b
+)
+;
+assert_array_equals
+(
+a
+.
+childNodes
+[
+b
 c
-c
+]
 )
+;
+a
+.
+moveBefore
+(
+c
 c
 )
 ;
@@ -2217,7 +2324,7 @@
 ;
 }
 "
-Inserting
+Moving
 a
 node
 before