Add a test to verify Request parameter is used

Author: jthacker

packages/openapi-fetch/test/common/request.test.ts

@@ -316,6 +316,30 @@ describe("request", () => {
     await client.GET("/resources");
   });
 
+  describe("custom Request", () => {
+    const ALL_METHODS = [["GET"], ["HEAD"], ["PUT"], ["POST"], ["DELETE"], ["OPTIONS"], ["PATCH"]] as const;
+
+    test.each(ALL_METHODS)("uses custom Request class - %s", async (method) => {
+      // sanity check to make sure the provided fetch function is actually called
+      expect.assertions(1);
+
+      class SpecialRequestImplementation extends Request { }
+
+      const customFetch = async (input: Request) => {
+        // make sure that the request is actually an instance of the custom request we provided
+        expect(input).instanceOf(SpecialRequestImplementation);
+        return Promise.resolve(Response.json({ hello: "world" }));
+      };
+
+      const client = createClient<paths>({
+        baseUrl: "https://fakeurl.example",
+        fetch: customFetch,
+      });
+
+      await (client as any)[method]("/resources", { Request: SpecialRequestImplementation });
+    });
+  });
+
   test("can attach custom properties to request", async () => {
     function createCustomFetch(data: any) {
       const response = {