feat(tests): add test for actual namespace passthrough

tests/CMakeLists.txt

@@ -9,5 +9,17 @@ include(doctest)
 add_executable(lbstd_version_tests test.cpp)
 target_link_libraries(lbstd_version_tests doctest::doctest lbstd_version)
 
+add_executable(lbstd_version_print_ns print_ns.cpp)
+target_link_libraries(lbstd_version_print_ns lbstd_version)
+
+# The manual test for namespace passthrough.
+set(LBSTD_VERSION_CMAKE_NS_PASSTHROUGH "CMake custom library namespace (\"${LBSTD_VERSION_NS}::\") passthrough in C++ code")
+add_test(NAME "${LBSTD_VERSION_CMAKE_NS_PASSTHROUGH}" COMMAND lbstd_version_print_ns)
+set_tests_properties("${LBSTD_VERSION_CMAKE_NS_PASSTHROUGH}" PROPERTIES
+  PASS_REGULAR_EXPRESSION "${LBSTD_VERSION_NS}"
+  LABELS "buildsystem"
+)
+
+# Auto-discoverable doctest unit tests
 doctest_discover_tests(lbstd_version_tests ADD_LABELS ON)
 

tests/print_ns.cpp

@@ -0,0 +1,20 @@
+// SPDX-FileCopyrightText: 2022 leha-bot and contributors
+//
+// SPDX-License-Identifier: BSL-1.0 OR BlueOak-1.0.0
+//
+// This executable is a smoke test for checking the proper namespace customizing via CMake's
+// -DLBSTD_VERSION_NS="namespace_name" configure parameter. The main() function just prints the
+// actual namespace which will be used in CMake's test check.
+#include <iostream>
+
+#include <version/version.hpp>
+
+#define MAKE_STRING(q) #q
+#define UNPACK_MACRO(q) q
+#define MAKE_STRING_FROM_MACRO(q) MAKE_STRING(q)
+
+int main()
+{
+	std::cout << MAKE_STRING_FROM_MACRO(LB_STD_VERSION_NS);
+	return 0;
+}