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

[tadjik1]

Description

Summary of Changes

Remove the emptyGetMore spy assertion from the NODE-6878 regression test. The test now only verifies that cursor.rewind() works correctly after cursor exhaustion via limit, which is the actual regression being guarded.

Notes for Reviewers

On MongoDB 9.0+, mongos now returns cursorId: 0 on the getMore that delivers the final batch when a limit is reached. This means the driver's emptyGetMore optimization (which avoids a wasted getMore when the server returns a non-zero cursorId after the limit is satisfied) is never triggered on sharded topologies with 9.0+.

The spy assertion required emptyGetMore to be called, which can no longer happen on 9.0. The original comment noted that without the spy, "this test always passes, even without the fix in NODE-6878" - that was true because if emptyGetMore was never called, the buggy (incomplete) response object was never used, so rewind() would succeed trivially. Now that the NODE-6878 fix is merged and emptyGetMore is a proper CursorResponse, the spy is no longer needed as a guard against a vacuously passing test. The rewind assertion remains meaningful regardless of which code path exhausts the cursor.

What is the motivation for this change?

Release Highlight

Release notes highlight

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[Copilot]

Pull request overview

This PR relaxes the NODE-6878 sharded regression test by removing the CursorResponse.emptyGetMore spy assertion, keeping the test focused on verifying that cursor.rewind() continues to work after the cursor is exhausted via limit.

Changes:

• Removed the CursorResponse.emptyGetMore spy/assertion from the sharded NODE-6878 regression test.
• Updated the test’s inline commentary to account for mongos behavior changes on MongoDB 9.0+.

Comments suppressed due to low confidence (1)

test/integration/crud/find.test.ts:1100

• After rewinding, the test only awaits cursor.toArray() without asserting anything about the returned documents. This can allow the test to pass even if rewind() results in an incorrectly empty/partial iteration (as long as no exception is thrown). Consider asserting the expected number of documents (e.g., 3 for limit: 3) and/or their contents, and updating the test description accordingly since it no longer validates CursorResponse.emptyGetMore fields.

      cursor.rewind();

      await cursor.toArray();
    }

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[dariakp]

@tadjik1 There are two failing tests still, do we have known tracking for either of them? The bson tests seem to be running an earlier version of the test - could you check on that?