C API: Value -> nix_value

tests/unit/libexpr/nix_api_value.cc

@@ -4,16 +4,26 @@
 #include "nix_api_util_internal.h"
 #include "nix_api_expr.h"
 #include "nix_api_value.h"
+#include "nix_api_expr_internal.h"
 
 #include "tests/nix_api_expr.hh"
 #include "tests/string_callback.hh"
 
 #include "gmock/gmock.h"
+#include <cstddef>
 #include <cstdlib>
 #include <gtest/gtest.h>
 
 namespace nixC {
 
+TEST_F(nix_api_expr_test, as_nix_value_ptr)
+{
+    // nix_alloc_value casts nix::Value to nix_value
+    // It should be obvious from the decl that that works, but if it doesn't,
+    // the whole implementation would be utterly broken.
+    ASSERT_EQ(sizeof(nix::Value), sizeof(nix_value));
+}
+
 TEST_F(nix_api_expr_test, nix_value_get_int_invalid)
 {
     ASSERT_EQ(0, nix_get_int(ctx, nullptr));