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  package org.eclipse.jgit.revwalk;
  
  import static org.junit.Assert.assertFalse;
  import static org.junit.Assert.assertTrue;
  
  import java.util.Arrays;
  import java.util.Optional;
  import java.util.stream.Stream;
  
  import org.eclipse.jgit.internal.storage.file.FileRepository;
  import org.eclipse.jgit.junit.LocalDiskRepositoryTestCase;
  import org.eclipse.jgit.junit.TestRepository;
  import org.junit.Before;
  import org.junit.Test;
  
  public abstract class ReachabilityCheckerTestCase
  		extends LocalDiskRepositoryTestCase {
  
  	protected abstract ReachabilityChecker getChecker(
  			TestRepository<FileRepository> repository) throws Exception;
  
  	TestRepository<FileRepository> repo;
  
  	/** {@inheritDoc} */
  	@Override
  	@Before
  	public void setUp() throws Exception {
  		super.setUp();
  		FileRepository db = createWorkRepository();
  		repo = new TestRepository<>(db);
  	}
  
  	@Test
  	public void reachable() throws Exception {
  		RevCommit a = repo.commit().create();
  		RevCommit b1 = repo.commit(a);
  		RevCommit b2 = repo.commit(b1);
  		RevCommit c1 = repo.commit(a);
  		RevCommit c2 = repo.commit(c1);
  		repo.update("refs/heads/checker", b2);
  
  		ReachabilityChecker checker = getChecker(repo);
  
  		assertReachable("reachable from one tip",
  				checker.areAllReachable(Arrays.asList(a), Stream.of(c2)));
  		assertReachable("reachable from another tip",
  				checker.areAllReachable(Arrays.asList(a), Stream.of(b2)));
  		assertReachable("reachable from itself",
  				checker.areAllReachable(Arrays.asList(a), Stream.of(b2)));
  	}
  
  	@Test
  	public void reachable_merge() throws Exception {
  		RevCommit a = repo.commit().create();
  		RevCommit b1 = repo.commit(a);
  		RevCommit b2 = repo.commit(b1);
  		RevCommit c1 = repo.commit(a);
 		RevCommit c2 = repo.commit(c1);
 		RevCommit merge = repo.commit(c2, b2);
 		repo.update("refs/heads/checker", merge);
 
 		ReachabilityChecker checker = getChecker(repo);
 
 		assertReachable("reachable through one branch",
 				checker.areAllReachable(Arrays.asList(b1),
 						Stream.of(merge)));
 		assertReachable("reachable through another branch",
 				checker.areAllReachable(Arrays.asList(c1),
 						Stream.of(merge)));
 		assertReachable("reachable, before the branching",
 				checker.areAllReachable(Arrays.asList(a),
 						Stream.of(merge)));
 	}
 
 	@Test
 	public void unreachable_isLaterCommit() throws Exception {
 		RevCommit a = repo.commit().create();
 		RevCommit b1 = repo.commit(a);
 		RevCommit b2 = repo.commit(b1);
 		repo.update("refs/heads/checker", b2);
 
 		ReachabilityChecker checker = getChecker(repo);
 
 		assertUnreachable("unreachable from the future",
 				checker.areAllReachable(Arrays.asList(b2), Stream.of(b1)));
 	}
 
 	@Test
 	public void unreachable_differentBranch() throws Exception {
 		RevCommit a = repo.commit().create();
 		RevCommit b1 = repo.commit(a);
 		RevCommit b2 = repo.commit(b1);
 		RevCommit c1 = repo.commit(a);
 		repo.update("refs/heads/checker", b2);
 
 		ReachabilityChecker checker = getChecker(repo);
 
 		assertUnreachable("unreachable from different branch",
 				checker.areAllReachable(Arrays.asList(c1), Stream.of(b2)));
 	}
 
 	@Test
 	public void reachable_longChain() throws Exception {
 		RevCommit root = repo.commit().create();
 		RevCommit head = root;
 		for (int i = 0; i < 10000; i++) {
 			head = repo.commit(head);
 		}
 		repo.update("refs/heads/master", head);
 
 		ReachabilityChecker checker = getChecker(repo);
 
 		assertReachable("reachable with long chain in the middle", checker
 				.areAllReachable(Arrays.asList(root), Stream.of(head)));
 	}
 
 	private static void assertReachable(String msg,
 			Optional<RevCommit> result) {
 		assertFalse(msg, result.isPresent());
 	}
 
 	private static void assertUnreachable(String msg,
 			Optional<RevCommit> result) {
 		assertTrue(msg, result.isPresent());
 	}
 }