fixed concept usage in zip and added zip tests

include/emlabcpp/zip.h

@@ -105,7 +105,7 @@ constexpr bool operator!=(const zip_iterator<Iterators...> &lh,
 /// ranges. If the size differs, increments of begin iterator will never be same
 /// as end iterator.
 //
-template <typename... Ts, std::enable_if_t<std::conjunction_v<is_container<Ts>...>> * = nullptr>
+template <range_container... Ts>
 inline auto zip(Ts &&... cont) {
         return view(zip_iterator(std::begin(cont)...), zip_iterator(std::end(cont)...));
 }

tests/CMakeLists.txt

@@ -47,5 +47,6 @@ add_emlabcpp_test(numeric_iterator_test)
 add_emlabcpp_test(access_iterator_test)
 add_emlabcpp_test(either_test)
 add_emlabcpp_test(physical_quantity_test)
+add_emlabcpp_test(zip_test)
 add_emlabcpp_test(static_vector_test)
 add_emlabcpp_test(pid_test)

tests/zip_test.cpp

+#include "emlabcpp/zip.h"
+
+#include <gtest/gtest.h>
+
+using namespace emlabcpp;
+
+TEST(zip, simple) {
+        std::vector<int> data = {1, 2, 3, 4, 5};
+
+        for (auto [lh, rh] : zip(data, data)) {
+                EXPECT_EQ(lh, rh);
+        }
+}