diff --git a/extensions/signal/src/client-adapter.test.ts b/extensions/signal/src/client-adapter.test.ts
index 9623e304c09..3637fc7db8a 100644
--- a/extensions/signal/src/client-adapter.test.ts
+++ b/extensions/signal/src/client-adapter.test.ts
@@ -95,12 +95,16 @@ function expectRpcCall(params: {
   if (params.rpcParams) {
     expectFields(requireRecord(rpcParams, "rpc params"), params.rpcParams);
   } else {
-    expect(rpcParams).toBeDefined();
+    if (rpcParams === undefined) {
+      throw new Error("expected rpc params argument");
+    }
   }
   if (params.options) {
     expectFields(requireRecord(options, "rpc options"), params.options);
   } else {
-    expect(options).toBeDefined();
+    if (options === undefined) {
+      throw new Error("expected rpc options argument");
+    }
   }
 }
 
diff --git a/extensions/signal/src/client-container.test.ts b/extensions/signal/src/client-container.test.ts
index ba75a33e0d0..2213e7094e6 100644
--- a/extensions/signal/src/client-container.test.ts
+++ b/extensions/signal/src/client-container.test.ts
@@ -288,7 +288,9 @@ describe("containerRestRequest", () => {
 
     // The timeout is enforced via AbortController, so we verify the call was made with a signal
     expect(mockFetch).toHaveBeenCalled();
-    expect(requireFetchCall()[1].signal).toBeDefined();
+    if (requireFetchCall()[1].signal === undefined) {
+      throw new Error("expected fetch call to include an abort signal");
+    }
   });
 });
 
@@ -428,7 +430,9 @@ describe("containerSendMessage", () => {
     const callArgs = mockFetch.mock.calls[0];
     const body = JSON.parse(callArgs[1].body);
     expect(body.attachments).toBeUndefined();
-    expect(body.base64_attachments).toBeDefined();
+    if (!Array.isArray(body.base64_attachments)) {
+      throw new Error("expected base64 attachments array");
+    }
     expect(body.base64_attachments).toHaveLength(1);
     expect(body.base64_attachments[0]).toMatch(
       /^data:image\/jpeg;filename=test-image\.jpg;base64,/,