test(NODE-7513): relax regression test for emptyGetMore (#4916)

Author: tadjik1

test/integration/crud/find.test.ts

@@ -3,7 +3,6 @@ import * as sinon from 'sinon';
 
 import {
   Code,
-  CursorResponse,
   Long,
   type MongoClient,
   MongoServerError,
@@ -1075,29 +1074,29 @@ describe('Find', function () {
   });
 
   it(
-    'regression test (NODE-6878): CursorResponse.emptyGetMore contains all CursorResponse fields',
+    'regression test (NODE-6878): cursor can be rewound after limit-based exhaustion',
     { requires: { topology: 'sharded' } },
     async function () {
       const collection = client.db('rewind-regression').collection('bar');
 
       await collection.deleteMany({});
       await collection.insertMany(Array.from({ length: 4 }, (_, i) => ({ x: i })));
 
-      const getMoreSpy = sinon.spy(CursorResponse, 'emptyGetMore', ['get']);
-
       const cursor = collection.find({}, { batchSize: 1, limit: 3 });
-      // emptyGetMore is used internally after limit + 1 documents have been iterated
+      // Iterate limit + 1 times to exercise the post-limit cursor path before rewind.
       await cursor.next();
       await cursor.next();
       await cursor.next();
       await cursor.next();
 
-      // assert that `emptyGetMore` is called.  if it is not, this test
-      // always passes, even without the fix in NODE-6878.
-      expect(getMoreSpy.get).to.have.been.called;
+      // On servers < 9.0, mongos returns a non-zero cursorId even after the limit
+      // is satisfied, so the driver uses CursorResponse.emptyGetMore to avoid a
+      // wasted getMore. On 9.0+, mongos returns cursorId: 0 when the limit is
+      // reached. In both cases, rewinding and re-iterating the cursor must work.
 
+      // rewind + toArray must not throw. Before the NODE-6878 fix,
+      // this would fail with a TypeError from emptyGetMore lacking CursorResponse fields.
       cursor.rewind();
-
       await cursor.toArray();
     }
   );