Add tests <fstream> addition and update CMake

test/CMakeLists.txt

@@ -97,6 +97,14 @@ if(CMAKE_CXX_COMPILER_ID MATCHES MSVC)
 endif()
 add_test(fwd_impl_test fwd_impl_test)
 
+if("cxx_std_17" IN_LIST GHC_FILESYSTEM_TEST_COMPILE_FEATURES)
+    add_executable(fs_std_header_test fs_std_header_test.cpp fs_std_fwd_header_test.cpp)
+    target_link_libraries(fs_std_header_test ghc_filesystem)
+    target_compile_features(fs_std_header_test PRIVATE cxx_std_17)
+    SetTestCompileOptions(fs_std_header_test)
+    add_test(fs_std_header_test fs_std_header_test)
+endif()
+
 add_executable(exception exception.cpp)
 if(NOT MSVC)
     target_compile_options(exception PRIVATE -fno-exceptions)

test/fs_std_fwd_header_test.cpp

@@ -0,0 +1,8 @@
+#define GHC_USE_STD_FS
+#include <ghc/fs_std_fwd.hpp>
+
+bool fs_std_fwd_header_test()
+{
+    fs::fstream stream;
+    return stream.is_open();
+}

test/fs_std_header_test.cpp

@@ -0,0 +1,10 @@
+#define GHC_USE_STD_FS
+#include <ghc/fs_std.hpp>
+
+bool fs_std_fwd_header_test();
+
+int main()
+{
+    fs::ifstream stream;
+    return stream.is_open() || fs_std_fwd_header_test() ? 1 : 0;
+}