migrate test server setup to separate file

test/testHelpers/fetchMockHelpers.ts

@@ -0,0 +1,41 @@
+import { jest } from "@jest/globals";
+
+/**
+ * Function to update behavior of the global `fetch` function.
+ * Note that the Passio GO API returns status code 200 for failed responses.
+ * @param obj
+ * @param status
+ */
+export function updateGlobalFetchMockJson(
+  obj: any,
+  status: number = 200
+) {
+  // @ts-ignore
+  global.fetch = jest.fn(() => {
+    return Promise.resolve({
+      json: () => Promise.resolve(obj),
+      status,
+      ok: status.toString().startsWith("2"), // 200-level codes are OK
+    })
+  });
+}
+
+/**
+ * Reset the global fetch function mock's JSON to return an empty object.
+ * @param obj
+ */
+export function resetGlobalFetchMockJson() {
+  updateGlobalFetchMockJson({});
+}
+
+
+export function updateGlobalFetchMockJsonToThrowSyntaxError() {
+  // @ts-ignore
+  global.fetch = jest.fn(() => {
+    return Promise.resolve({
+      json: () => Promise.reject(new SyntaxError("Unable to parse JSON")),
+      status: 200,
+      ok: true,
+    })
+  }) as jest.Mock;
+}