diff --git a/cadence/tests/uint64_linked_list_test.cdc b/cadence/tests/uint64_linked_list_test.cdc
new file mode 100644
index 00000000..4ad47b0b
--- /dev/null
+++ b/cadence/tests/uint64_linked_list_test.cdc
@@ -0,0 +1,154 @@
+import Test
+import "UInt64LinkedList"
+
+access(all) fun setup() {
+    let err = Test.deployContract(
+        name: "UInt64LinkedList",
+        path: "../contracts/UInt64LinkedList.cdc",
+        arguments: []
+    )
+    Test.expect(err, Test.beNil())
+}
+
+// ─── Tests ───────────────────────────────────────────────────────────────────
+
+access(all) fun test_EmptyListState() {
+    let list <- UInt64LinkedList.createList()
+    Test.assert(list.head == nil)
+    Test.assert(list.tail == nil)
+    Test.assert(!list.contains(id: 1))
+    destroy list
+}
+
+access(all) fun test_InsertSingle() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 42)
+    Test.assert(list.contains(id: 42))
+    Test.assert(list.head == 42)
+    Test.assert(list.tail == 42)
+    destroy list
+}
+
+access(all) fun test_InsertMultiple_HeadAndTailOrder() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 1)
+    list.insertAtHead(id: 2)
+    list.insertAtHead(id: 3)
+    // head = 3 (most recent), tail = 1 (oldest)
+    Test.assert(list.head == 3)
+    Test.assert(list.tail == 1)
+    destroy list
+}
+
+access(all) fun test_Contains() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 10)
+    list.insertAtHead(id: 20)
+    Test.assert(list.contains(id: 10))
+    Test.assert(list.contains(id: 20))
+    Test.assert(!list.contains(id: 99))
+    destroy list
+}
+
+access(all) fun test_RemoveSingle() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 7)
+    Test.assert(list.remove(id: 7))
+    Test.assert(list.head == nil)
+    Test.assert(list.tail == nil)
+    Test.assert(!list.contains(id: 7))
+    destroy list
+}
+
+access(all) fun test_RemoveHead() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 1)
+    list.insertAtHead(id: 2)
+    list.insertAtHead(id: 3)
+    // list: 3 <-> 2 <-> 1  (head=3, tail=1)
+    Test.assert(list.remove(id: 3))
+    // list: 2 <-> 1
+    Test.assert(list.head == 2)
+    Test.assert(list.tail == 1)
+    destroy list
+}
+
+access(all) fun test_RemoveTail() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 1)
+    list.insertAtHead(id: 2)
+    list.insertAtHead(id: 3)
+    // list: 3 <-> 2 <-> 1  (head=3, tail=1)
+    Test.assert(list.remove(id: 1))
+    // list: 3 <-> 2
+    Test.assert(list.head == 3)
+    Test.assert(list.tail == 2)
+    destroy list
+}
+
+access(all) fun test_RemoveMiddle() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 1)
+    list.insertAtHead(id: 2)
+    list.insertAtHead(id: 3)
+    // list: 3 <-> 2 <-> 1
+    Test.assert(list.remove(id: 2))
+    // list: 3 <-> 1
+    Test.assert(list.head == 3)
+    Test.assert(list.tail == 1)
+    Test.assert(!list.contains(id: 2))
+    Test.assert(list.contains(id: 3))
+    Test.assert(list.contains(id: 1))
+    destroy list
+}
+
+access(all) fun test_RemoveAbsent() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 5)
+    Test.assert(!list.remove(id: 999))
+    destroy list
+}
+
+access(all) fun test_RemoveFromEmpty() {
+    let list <- UInt64LinkedList.createList()
+    Test.assert(!list.remove(id: 42))
+    destroy list
+}
+
+access(all) fun test_TailWalk_Order() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 1)
+    list.insertAtHead(id: 2)
+    list.insertAtHead(id: 3)
+    // head=3, tail=1 → tailWalk yields [1, 2, 3]
+    let walked = list.tailWalk(limit: 10)
+    destroy list
+    let expected: [UInt64] = [1, 2, 3]
+    Test.assertEqual(expected, walked)
+}
+
+access(all) fun test_TailWalk_Limit() {
+    let list <- UInt64LinkedList.createList()
+    list.insertAtHead(id: 1)
+    list.insertAtHead(id: 2)
+    list.insertAtHead(id: 3)
+    let walked = list.tailWalk(limit: 2)
+    destroy list
+    Test.assertEqual(2, walked.length)
+}
+
+access(all) fun test_TailWalk_Empty() {
+    let list <- UInt64LinkedList.createList()
+    let walked = list.tailWalk(limit: 5)
+    destroy list
+    Test.assertEqual(0, walked.length)
+}
+
+access(all) fun test_InsertDuplicate_Panics() {
+    Test.expectFailure(fun() {
+        let list <- UInt64LinkedList.createList()
+        list.insertAtHead(id: 1)
+        list.insertAtHead(id: 1)
+        destroy list
+    }, errorMessageSubstring: "ID already exists in list")
+}