should be it

external/duckdb/tools/juliapkg/test/test_c_api.jl

@@ -0,0 +1,12 @@
+
+@testset "C API Type Checks" begin
+
+    # Check struct sizes.
+    # Timestamp struct size mismatch, eventually structs are stored as pointers. This happens if they are declared as mutable structs.
+    @test sizeof(DuckDB.duckdb_timestamp_struct) ==
+          sizeof(DuckDB.duckdb_date_struct) + sizeof(DuckDB.duckdb_time_struct)
+
+    # Bot structs are equivalent and actually stored as a Union type in C.
+    @test sizeof(DuckDB.duckdb_string_t) == sizeof(DuckDB.duckdb_string_t_ptr)
+
+end