diff --git a/frontend/src/setupTests.ts b/frontend/src/setupTests.ts
index d0de870..3de2908 100644
--- a/frontend/src/setupTests.ts
+++ b/frontend/src/setupTests.ts
@@ -1 +1,14 @@
 import "@testing-library/jest-dom";
+import { beforeEach, vi } from "vitest";
+
+// Provide a default fetch mock so components that call API endpoints on mount
+// don't throw URL-parse errors in the jsdom test environment.  Tests that need
+// specific responses should mock the relevant `api.*` method as usual.
+beforeEach(() => {
+	vi.stubGlobal(
+		"fetch",
+		vi.fn(() =>
+			Promise.resolve(new Response(JSON.stringify({}), { status: 200 })),
+		),
+	);
+});
diff --git a/frontend/vitest.config.ts b/frontend/vitest.config.ts
index f77f4f2..12c61cb 100644
--- a/frontend/vitest.config.ts
+++ b/frontend/vitest.config.ts
@@ -8,6 +8,11 @@ export default defineConfig({
   },
   test: {
     environment: "jsdom",
+    environmentOptions: {
+      jsdom: {
+        url: "http://localhost:3000",
+      },
+    },
     globals: true,
     testTimeout: 10_000,
     setupFiles: ["./src/setupTests.ts"],