An incomplete shard snapshot will prevent a shard from moving away from a node (see `SnapshotInProgressAllocationDecider`). That means that when a shard snapshot completes it may become possible to perform some shard movements that previously were not possible, so we should trigger a reroute to start those movements. AFAICT we do not trigger such a reroute today.
test/framework/src/main/java/org/elasticsearch/test/ESTestCase.java
import org.apache.logging.log4j.status.StatusData;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.lucene.tests.util.LuceneTestCase;
import org.apache.lucene.tests.util.LuceneTestCase.SuppressCodecs;
import org.apache.lucene.tests.util.TestRuleMarkFailure;
import org.apache.lucene.tests.util.TestUtil;
import org.apache.lucene.tests.util.TimeUnits;
import org.apache.lucene.util.SetOnce;
import org.elasticsearch.TransportVersion;
import org.elasticsearch.bootstrap.BootstrapForTesting;
import org.elasticsearch.client.internal.Requests;
import org.elasticsearch.cluster.ClusterModule;
import org.elasticsearch.cluster.metadata.IndexMetadata;
import org.elasticsearch.common.bytes.BytesArray;
import org.elasticsearch.common.bytes.BytesReference;
import org.elasticsearch.common.bytes.CompositeBytesReference;
import org.elasticsearch.common.io.stream.BytesStreamOutput;
import org.elasticsearch.common.io.stream.NamedWriteable;
import org.elasticsearch.common.io.stream.NamedWriteableAwareStreamInput;
import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
import org.elasticsearch.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.common.logging.DeprecationLogger;
import org.elasticsearch.common.logging.HeaderWarning;
import org.elasticsearch.common.logging.HeaderWarningAppender;
import org.elasticsearch.common.logging.LogConfigurator;
import org.elasticsearch.common.logging.Loggers;
import org.elasticsearch.common.lucene.Lucene;
import org.elasticsearch.common.settings.Setting;