Added linkedlist_delete, funtions by index, one test was added and passed for checking when eliminate head, subsequent commits will add more tests for this function

tests/test_linkedlist.c

@@ -7,7 +7,7 @@
 #include <setjmp.h>
 #include <cmocka.h>
 
-static void linkedlist_test_append(void **state) {
+static void linkedlist_test_append_3_int(void **state) {
     (void) state;
 
     LinkedList *ll;
@@ -23,9 +23,30 @@ static void linkedlist_test_append(void **state) {
     linkedlist_destroy(ll);
 }
 
+static void linkedlist_test_delete_head(void **state) {
+    (void) state;
+
+    LinkedList *ll;
+    linkedlist_create(&ll, sizeof(int));
+    for (int i = 0; i < 3; i++) {
+        linkedlist_append(ll, &i);
+    }
+    linkedlist_delete(ll, 0);
+    size_t len;
+    linkedlist_len(ll,&len);
+    assert_int_equal(len, 2);
+    for (int i = 0; i < 2; i++) {
+        int n;
+        linkedlist_get(ll, i, &n);
+        assert_int_equal(n, i + 1);
+    }
+    linkedlist_destroy(ll);
+}
+
 int main(void) {
     const struct CMUnitTest tests[] = {
-        cmocka_unit_test(linkedlist_test_append),
+        cmocka_unit_test(linkedlist_test_append_3_int),
+        cmocka_unit_test(linkedlist_test_delete_head),
     };
 
     return cmocka_run_group_tests(tests, NULL, NULL);