diff --git a/packages/core/test/ClientTest.ts b/packages/core/test/ClientTest.ts
index 7ffe8d1aa..ddb74c4ce 100644
--- a/packages/core/test/ClientTest.ts
+++ b/packages/core/test/ClientTest.ts
@@ -171,8 +171,8 @@ class TDClient implements ProtocolClient {
         return "TDClient";
     }
 
-    discoverDirectly(uri: string): Promise<Content> {
-        return Promise.reject(new Error("discoverDirectly not implemented"));
+    async discoverDirectly(uri: string): Promise<Content> {
+        throw new Error("discoverDirectly not implemented.");
     }
 }
 
@@ -249,8 +249,8 @@ class TrapClient implements ProtocolClient {
 
     public setSecurity = (metadata: SecurityScheme[]) => false;
 
-    discoverDirectly(uri: string): Promise<Content> {
-        return Promise.reject(new Error("discoverDirectly not implemented"));
+    async discoverDirectly(uri: string): Promise<Content> {
+        throw new Error("discoverDirectly not implemented.");
     }
 }
 
@@ -316,8 +316,8 @@ class TestProtocolClient implements ProtocolClient {
         return true;
     }
 
-    discoverDirectly(uri: string): Promise<Content> {
-        return Promise.reject(new Error("discoverDirectly not implemented"));
+    async discoverDirectly(uri: string): Promise<Content> {
+        throw new Error("discoverDirectly not implemented.");
     }
 }