1 files changed, 33 insertions, 0 deletions
diff --git a/json4cpp/tests/abi/config/custom.cpp b/json4cpp/tests/abi/config/custom.cpp
new file mode 100644
index 0000000000..0097747c98
--- /dev/null
+++ b/json4cpp/tests/abi/config/custom.cpp
@@ -0,0 +1,33 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#include "doctest_compatibility.h"
+
+#include "config.hpp"
+
+// define custom namespace
+#define NLOHMANN_JSON_NAMESPACE nlohmann // this line may be omitted
+#define NLOHMANN_JSON_NAMESPACE_BEGIN namespace nlohmann {
+#define NLOHMANN_JSON_NAMESPACE_END }
+#include <nlohmann/json_fwd.hpp>
+
+TEST_CASE("custom namespace")
+{
+    // GCC 4.8 fails with regex_error
+#if !DOCTEST_GCC || DOCTEST_GCC >= DOCTEST_COMPILER(4, 9, 0)
+    SECTION("namespace matches expectation")
+    {
+        std::string expected = "nlohmann::basic_json";
+
+        // fallback for Clang
+        const std::string ns{STRINGIZE(NLOHMANN_JSON_NAMESPACE) "::basic_json"};
+
+        CHECK(namespace_name<nlohmann::json>(ns) == expected);
+    }
+#endif
+}