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 java.util.Set;
import java.util.TimeZone;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.BooleanSupplier;
import java.util.function.Consumer;
import java.util.function.IntFunction;
import java.util.function.Predicate;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import java.util.stream.Stream;
import static java.util.Collections.emptyMap;
import static org.elasticsearch.common.util.CollectionUtils.arrayAsArrayList;
import static org.hamcrest.Matchers.anyOf;
import static org.hamcrest.Matchers.contains;
import static org.hamcrest.Matchers.empty;
import static org.hamcrest.Matchers.emptyCollectionOf;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.hasItem;
import static org.hamcrest.Matchers.startsWith;
/**
 * Base testcase for randomized unit testing with Elasticsearch
 */