test(web): align jsdom abort signals with Node

apps/web/src/test/setup.spec.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from 'vitest';
+
+describe('Vitest abort-controller realm', () => {
+  it('provides a global signal accepted by Node native Request', () => {
+    const controller = new AbortController();
+    const request = new Request('https://mosaic.invalid/navigation', {
+      signal: controller.signal,
+    });
+
+    expect(request.signal).toBeInstanceOf(AbortSignal);
+    controller.abort();
+    expect(request.signal.aborted).toBe(true);
+  });
+});

apps/web/src/test/setup.ts

@@ -0,0 +1,23 @@
+import { transferableAbortController } from 'node:util';
+
+// jsdom installs realm-local abort constructors while Node's undici Request
+// remains native. React Router passes a global AbortSignal to Request, so both
+// constructors must come from Node's native realm during tests.
+const nativeController = transferableAbortController();
+const nativeAbortController = nativeController.constructor;
+const nativeAbortSignal = nativeController.signal.constructor;
+
+for (const target of [globalThis, window]) {
+  Object.defineProperties(target, {
+    AbortController: {
+      configurable: true,
+      writable: true,
+      value: nativeAbortController,
+    },
+    AbortSignal: {
+      configurable: true,
+      writable: true,
+      value: nativeAbortSignal,
+    },
+  });
+}

apps/web/vitest.config.ts

@@ -14,6 +14,8 @@ export default defineConfig({
   test: {
     globals: true,
     environment: 'jsdom',
+    setupFiles: ['./src/test/setup.ts'],
+    isolate: true,
     exclude: ['e2e/**', 'node_modules/**'],
   },
 });