test: Fix getEventPayloads e2e test helper

The test helper `getEventPayloads` is meant to wait until all mock
endpoints provided have resolved (i.e. until none are pending).
However, it currently only waits until the _last_ mock endpoint in the
array has been fulfilled. The pending status of the others is ignored.
This results in race conditions, because the status of non-last mock
endpoints is indeterminate when this returns.

The `hasRequest` parameter has been renamed to `waitWhilePending` to
make the expected behavior more clear, and JSDocs have been added for
each parameter.

test/e2e/helpers.js

@@ -725,23 +725,30 @@ async function switchToNotificationWindow(driver) {
  *
  * @param {WebDriver} driver
  * @param {import('mockttp').MockedEndpoint[]} mockedEndpoints
- * @param {boolean} hasRequest
+ * @param {boolean} [waitWhilePending] - Wait until no requests are pending
  * @returns {Promise<import('mockttp/dist/pluggable-admin').MockttpClientResponse[]>}
  */
-async function getEventPayloads(driver, mockedEndpoints, hasRequest = true) {
-  await driver.wait(
-    async () => {
-      let isPending = true;
-
-      for (const mockedEndpoint of mockedEndpoints) {
-        isPending = await mockedEndpoint.isPending();
-      }
+async function getEventPayloads(
+  driver,
+  mockedEndpoints,
+  waitWhilePending = true,
+) {
+  if (waitWhilePending) {
+    await driver.wait(
+      async () => {
+        const pendingStatuses = await Promise.all(
+          mockedEndpoints.map((mockedEndpoint) => mockedEndpoint.isPending()),
+        );
+        const isSomethingPending = pendingStatuses.some(
+          (pendingStatus) => pendingStatus,
+        );
 
-      return isPending === !hasRequest;
-    },
-    driver.timeout,
-    true,
-  );
+        return !isSomethingPending;
+      },
+      driver.timeout,
+      true,
+    );
+  }
   const mockedRequests = [];
   for (const mockedEndpoint of mockedEndpoints) {
     mockedRequests.push(...(await mockedEndpoint.getSeenRequests()));