tests: add autoping, helpers and XEP functional tests

- Add 15 unit tests for autoping logic (XEP-0199)
- Add 10 helper tests for refactoring validation
- Add Last Activity functional tests (XEP-0012)
- Add MUC affiliation/kick tests (XEP-0045)

tests/unittests/test_helpers.h

@@ -0,0 +1,25 @@
+/*
+ * test_helpers.h
+ * Header for helper function tests
+ */
+
+#ifndef TEST_HELPERS_H
+#define TEST_HELPERS_H
+
+/* Subwindow width clamping tests */
+void test_subwin_width_clamps_to_min(void** state);
+void test_subwin_width_clamps_to_max(void** state);
+void test_subwin_width_valid_unchanged(void** state);
+void test_subwin_width_small_cols(void** state);
+
+/* Hash table iteration tests */
+void test_hash_table_iter_finds_all_keys(void** state);
+void test_hash_table_iter_empty_table(void** state);
+void test_hash_table_iter_early_exit(void** state);
+void test_nested_hash_table_feature_lookup(void** state);
+
+/* Bug fix verification tests */
+void test_calloc_array_iteration_bug(void** state);
+void test_format_string_with_percent(void** state);
+
+#endif