Ok, corrected insert, should have copied directly from my c implementation, all tests good, just need to test insert middle

test/test_linkedlist.cpp

@@ -279,3 +279,25 @@ TEST_CASE("Insert at start of list", "[linkedlist]") {
     REQUIRE(list.len() == 4);
     REQUIRE(list.get(0) == 90);
 }
+
+TEST_CASE("Insert at end of list", "[linkedlist]") {
+    LinkedList<int> list = {};
+
+    REQUIRE(list.len() == 0);
+
+    list.append(8);
+    REQUIRE(list.len() == 1);
+    REQUIRE(list.get(0) == 8);
+
+    list.append(9);
+    REQUIRE(list.len() == 2);
+    REQUIRE(list.get(1) == 9);
+
+    list.append(10);
+    REQUIRE(list.len() == 3);
+    REQUIRE(list.get(2) == 10);
+
+    list.insert(2, 90);
+    REQUIRE(list.len() == 4);
+    REQUIRE(list.get(2) == 90);
+}