diff --git a/xo-arena/utest/DArenaVector.test.cpp b/xo-arena/utest/DArenaVector.test.cpp
index dc6a32c9..2deca944 100644
--- a/xo-arena/utest/DArenaVector.test.cpp
+++ b/xo-arena/utest/DArenaVector.test.cpp
@@ -68,6 +68,48 @@ namespace xo {
             REQUIRE(vec[1] == 20.0);
             REQUIRE(vec[2] == 30.0);
         }
+
+        TEST_CASE("DArenaVector-at-valid", "[arena][DArenaVector]")
+        {
+            ArenaConfig cfg { .name_ = "testarena",
+                              .size_ = 4096 };
+            DArenaVector<double> vec = DArenaVector<double>::map(cfg);
+
+            vec.push_back(100.0);
+            vec.push_back(200.0);
+            vec.push_back(300.0);
+
+            REQUIRE(vec.at(0) == 100.0);
+            REQUIRE(vec.at(1) == 200.0);
+            REQUIRE(vec.at(2) == 300.0);
+
+            // test mutability via at()
+            vec.at(1) = 250.0;
+            REQUIRE(vec.at(1) == 250.0);
+        }
+
+        TEST_CASE("DArenaVector-at-throws", "[arena][DArenaVector]")
+        {
+            ArenaConfig cfg { .name_ = "testarena",
+                              .size_ = 4096 };
+            DArenaVector<double> vec = DArenaVector<double>::map(cfg);
+
+            // empty vector - any index is invalid
+            REQUIRE_THROWS_AS(vec.at(0), std::out_of_range);
+
+            vec.push_back(1.0);
+            vec.push_back(2.0);
+
+            // valid indices work
+            REQUIRE_NOTHROW(vec.at(0));
+            REQUIRE_NOTHROW(vec.at(1));
+
+            // index == size is invalid
+            REQUIRE_THROWS_AS(vec.at(2), std::out_of_range);
+
+            // index > size is invalid
+            REQUIRE_THROWS_AS(vec.at(100), std::out_of_range);
+        }
     }
 }