diff --git a/test/core/thing_description_test.dart b/test/core/thing_description_test.dart
index c156d7a9..20c72926 100644
--- a/test/core/thing_description_test.dart
+++ b/test/core/thing_description_test.dart
@@ -74,21 +74,93 @@ void main() {
       );
     });
 
-    test("use the correct @context entry as the default prefix value", () {
-      final thingDescription = {
+    test("reject invalid ComboSecuritySchemes", () {
+      final invalidThingDescription1 = {
         "@context": [
           "https://www.w3.org/2022/wot/td/v1.1",
         ],
         "title": "Invalid TD with missing security field.",
-        "security": "nosec_sc",
+        "security": "combo_sc",
         "securityDefinitions": {
-          "nosec_sc": {"scheme": "nosec"},
+          "combo_sc": {"scheme": "combo"},
         },
-      }.toThingDescription();
+      };
 
       expect(
-        thingDescription.prefixMapping.defaultPrefixValue,
-        "https://www.w3.org/2022/wot/td/v1.1",
+        invalidThingDescription1.toThingDescription,
+        throwsFormatException,
+      );
+
+      final invalidThingDescription2 = {
+        "@context": [
+          "https://www.w3.org/2022/wot/td/v1.1",
+        ],
+        "title": "Invalid TD with missing security field.",
+        "security": "combo_sc",
+        "securityDefinitions": {
+          "nosec_sc1": {"scheme": "nosec"},
+          "nosec_sc2": {"scheme": "nosec"},
+          "combo_sc": {
+            "scheme": "combo",
+            "oneOf": [
+              "nosec_sc1",
+              "nosec_sc2",
+            ],
+            "allOf": [
+              "nosec_sc1",
+              "nosec_sc2",
+            ],
+          },
+        },
+      };
+
+      expect(
+        invalidThingDescription2.toThingDescription,
+        throwsFormatException,
+      );
+
+      final invalidThingDescription3 = {
+        "@context": [
+          "https://www.w3.org/2022/wot/td/v1.1",
+        ],
+        "title": "Invalid TD with missing security field.",
+        "security": "combo_sc",
+        "securityDefinitions": {
+          "nosec_sc1": {"scheme": "nosec"},
+          "combo_sc": {
+            "scheme": "combo",
+            "oneOf": [
+              "nosec_sc1",
+            ],
+          },
+        },
+      };
+
+      expect(
+        invalidThingDescription3.toThingDescription,
+        throwsFormatException,
+      );
+
+      final invalidThingDescription4 = {
+        "@context": [
+          "https://www.w3.org/2022/wot/td/v1.1",
+        ],
+        "title": "Invalid TD with missing security field.",
+        "security": "combo_sc",
+        "securityDefinitions": {
+          "nosec_sc1": {"scheme": "nosec"},
+          "combo_sc": {
+            "scheme": "combo",
+            "allOf": [
+              "nosec_sc1",
+            ],
+          },
+        },
+      };
+
+      expect(
+        invalidThingDescription4.toThingDescription,
+        throwsFormatException,
       );
     });
   });