Support relative urls

src/index.ts

@@ -309,6 +309,21 @@ function requestNotMatches(request: Request, urlOrPredicate: UrlOrPredicate): bo
   return !requestMatches(request, urlOrPredicate);
 }
 
+// Node 18 does not support URL.canParse()
+export function canParseURL(url: string): boolean {
+  try {
+    new URL(url);
+    return true;
+  } catch (err) {
+    return false;
+  }
+}
+
+// Node Requests cannot be relative
+function resolveInput(input: string): string {
+  return typeof location !== 'undefined' && !canParseURL(input) ? new URL(input, location.origin).toString() : input;
+}
+
 function normalizeRequest(input: RequestInput, requestInit?: RequestInit): Request {
   if (input instanceof Request) {
     if (input.signal && input.signal.aborted) {
@@ -319,12 +334,12 @@ function normalizeRequest(input: RequestInput, requestInit?: RequestInit): Reque
     if (requestInit && requestInit.signal && requestInit.signal.aborted) {
       abort();
     }
-    return new Request(input, requestInit);
+    return new Request(resolveInput(input), requestInit);
   } else {
     if (requestInit && requestInit.signal && requestInit.signal.aborted) {
       abort();
     }
-    return new Request(input.toString(), requestInit);
+    return new Request(resolveInput(input.toString()), requestInit);
   }
 }
 

tests/api.test.ts

@@ -100,6 +100,14 @@ describe('testing mockResponse', () => {
     expect(fetch.mock.calls[0]![0]).toEqual(new URL('https://instagram.com'));
   });
 
+  it('should support relative request urls', async () => {
+    fetch.mockResponseOnce(JSON.stringify({ data: 'abcde' }), { status: 200 });
+
+    const response = await fetch('folder/file.json').then((res) => res.json());
+
+    expect(response).toEqual({ data: 'abcde' });
+  });
+
   it('should allow empty response bodies', async () => {
     fetch.mockResponseOnce(null, { status: 204 });
     fetch.mockResponseOnce(undefined, { status: 204 });

tsconfig.json

@@ -3,7 +3,8 @@
     "module": "NodeNext",
     "moduleResolution": "NodeNext",
     "lib": [
-      "es2022"
+      "es2022",
+      "dom",
     ],
     "baseUrl": "./",
     "paths": {

vitest.config.ts

@@ -6,4 +6,7 @@ export default defineConfig({
       'vitest-fetch-mock': './src/index',
     },
   },
+  test: {
+    environment: 'jsdom',
+  },
 });