The test compares the result of listShard with the result of getShardMap.
When listShard and getShardMap run against different mongos might report different results.

Specifically, getShardMap is empty. 
This is probably due to staleness as getShardMap relies on the shardRegistry
The issue is rare, so you need to repeat the test multiple times to reproduce 

The goal of the ticket should be to define whether

• this is an issue
• the test requires modifications to ensure the shard registry is not stale
• this is not an issue but it's fine for the test to run against a pinned mongos (current solution)