test(furvm): introduce an add things test

furvm/test/test.cpp

@@ -1,3 +1,28 @@
+#include "furlang/arena.hpp"
+#include "furvm/furvm.hpp"
+#include "furvm/thing.hpp"
+#include "furvm/thing_allocator.hpp"
+
 #include "gtest/gtest.h" // IWYU pragma: keep
 
-namespace {}
+namespace {
+
+// TODO: Basic program tests (e.g. for loops)
+
+TEST(Things, Ops) {
+    furlang::arena                    arena;
+    furvm::thing_allocator<std::byte> alloc{ arena };
+
+    furvm::thing lhs{ furvm::thing_type{ furvm::thing_type::U32 }, alloc };
+    lhs.get<furvm::thing_type::u32>() = 6;
+    furvm::thing rhs{ furvm::thing_type{ furvm::thing_type::U32 }, alloc };
+    rhs.get<furvm::thing_type::u32>() = 7;
+
+    auto res = lhs.add(rhs);
+    ASSERT_EQ(res.type().type, furvm::thing_type::U32);
+    EXPECT_EQ(lhs.get<furvm::thing_type::u32>(), 6);
+    EXPECT_EQ(rhs.get<furvm::thing_type::u32>(), 7);
+    EXPECT_EQ(res.get<furvm::thing_type::u32>(), 6 + 7);
+}
+
+} // namespace