### Question:
AwsRDSPlatform extends Platform { public Set<String> getClusterInstances (String dbClusterIdentifier) { log.info("Getting cluster instances for {}", keyValue(AWS_RDS_CLUSTER_DATADOG_IDENTIFIER, dbClusterIdentifier)); return amazonRDS.describeDBClusters(new DescribeDBClustersRequest().withDBClusterIdentifier(dbClusterIdentifier)) .getDBClusters() .stream() .map(DBCluster::getDBClusterMembers) .flatMap(Collection::stream) .map(DBClusterMember::getDBInstanceIdentifier) .collect(toSet()); } @Autowired  AwsRDSPlatform();   AwsRDSPlatform(AmazonRDS amazonRDS, AmazonEC2 amazonEC2); Map<String, String> getVpcToSecurityGroupMap(); @Override ApiStatus getApiStatus(); @Override PlatformLevel getPlatformLevel(); @Override PlatformHealth getPlatformHealth(); @Override List<Container> generateExperimentRoster(); @Override boolean isContainerRecycled(Container container); Map<String, String> getFilter(); void setFilter(Map<String, String> filter); void failoverCluster(String dbClusterIdentifier); void restartInstance(String... dbInstanceIdentifiers); Set<String> getClusterInstances(String dbClusterIdentifier); ContainerHealth getInstanceStatus(String... dbInstanceIdentifiers); void setVpcSecurityGroupIds(String dbInstanceIdentifier, String vpcSecurityGroupId); void setVpcSecurityGroupIds(String dbInstanceIdentifier, Collection<String> vpcSecurityGroupIds); ContainerHealth checkVpcSecurityGroupIds(String dbInstanceIdentifier, Collection<String> vpcSecurityGroupIds); Collection<String> getVpcSecurityGroupIds(String dbInstanceIdentifier); String getChaosSecurityGroup(String dbInstanceIdentifier); DBSnapshot snapshotDBInstance(String dbInstanceIdentifier); DBClusterSnapshot snapshotDBCluster(String dbClusterIdentifier); void deleteInstanceSnapshot(DBSnapshot dbSnapshot); void deleteClusterSnapshot(DBClusterSnapshot dbClusterSnapshot); boolean isInstanceSnapshotRunning(String dbInstanceIdentifier); boolean isClusterSnapshotRunning(String dbClusterIdentifier);  }### Answer:
@Test public void getClusterInstances () { String instanceId1 = randomUUID().toString(); String instanceId2 = randomUUID().toString(); String clusterId = randomUUID().toString(); DescribeDBClustersResult dbClustersResult = new DescribeDBClustersResult().withDBClusters(new DBCluster().withDBClusterMembers(new DBClusterMember() .withDBInstanceIdentifier(instanceId1), new DBClusterMember().withDBInstanceIdentifier(instanceId2))); doReturn(dbClustersResult).when(amazonRDS).describeDBClusters(new DescribeDBClustersRequest().withDBClusterIdentifier(clusterId)); assertThat(awsRDSPlatform.getClusterInstances(clusterId), IsIterableContainingInAnyOrder.containsInAnyOrder(instanceId1, instanceId2)); }