xo-object2: beginning of DString + utest

utest/DString.test.cpp

@@ -0,0 +1,36 @@
+/** @file DString.test.cpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#include <xo/object2/DString.hpp>
+#include <xo/alloc2/arena/IAllocator_DArena.hpp>
+#include <catch2/catch.hpp>
+
+namespace xo {
+    using xo::scm::DString;
+    using xo::mm::AAllocator;
+    using xo::mm::DArena;
+    using xo::mm::ArenaConfig;
+    using xo::facet::with_facet;
+    using xo::facet::obj;
+
+    namespace ut {
+        TEST_CASE("DString-empty", "[object2][DString]")
+        {
+            ArenaConfig cfg { .name_ = "testarena",
+                              .size_ = 4*1024 };
+            DArena arena = DArena::map(cfg);
+            auto alloc = with_facet<AAllocator>::mkobj(&arena);
+
+            DString * s = DString::empty(alloc, 16);
+
+            REQUIRE(s != nullptr);
+            REQUIRE(s->capacity() == 16);
+            REQUIRE(s->size() == 0);
+            REQUIRE(s->chars()[0] == '\0');
+        }
+    } /*namespace ut*/
+} /*namespace xo*/
+
+/* end DString.test.cpp */