Properly close all files when dealing with archives (#1274)

* Properly close all files when dealing with archives

* Move file utils to SafeFiles class

* Licenses

(cherry picked from commit a600266d41151eec4f2239cf90e202bb99fa3a8b)

worldedit-core/src/test/java/com/sk89q/worldedit/world/snapshot/experimental/fs/FSSDContext.java

@@ -0,0 +1,104 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.world.snapshot.experimental.fs;
+
+import com.sk89q.worldedit.util.io.Closer;
+import com.sk89q.worldedit.util.io.file.ArchiveDir;
+import com.sk89q.worldedit.util.io.file.ArchiveNioSupport;
+import com.sk89q.worldedit.world.snapshot.experimental.Snapshot;
+
+import javax.annotation.Nullable;
+import java.io.IOException;
+import java.net.URI;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.stream.Stream;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static java.util.stream.Collectors.toList;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Context class for using a {@link FileSystemSnapshotDatabase}.
+ */
+class FSSDContext {
+
+    final ArchiveNioSupport archiveNioSupport;
+    final FileSystemSnapshotDatabase db;
+
+    FSSDContext(ArchiveNioSupport archiveNioSupport, Path root) {
+        this.archiveNioSupport = archiveNioSupport;
+        this.db = new FileSystemSnapshotDatabase(root, archiveNioSupport);
+    }
+
+    Path path(String first, String... more) {
+        Path p = db.getRoot().resolve(Paths.get(first, more));
+        checkArgument(p.startsWith(db.getRoot()), "Escaping root!");
+        return p;
+    }
+
+    URI nameUri(String name) {
+        return FileSystemSnapshotDatabase.createUri(name);
+    }
+
+    Snapshot requireSnapshot(String name) throws IOException {
+        return requireSnapshot(name, db.getSnapshot(nameUri(name)).orElse(null));
+    }
+
+    Snapshot requireListsSnapshot(String name) throws IOException {
+        // World name is the last element of the path
+        String worldName = Paths.get(name).getFileName().toString();
+        // Without an extension
+        worldName = worldName.split("\\.")[0];
+        List<Snapshot> snapshots;
+        try (Stream<Snapshot> snapshotStream = db.getSnapshots(worldName)) {
+            snapshots = snapshotStream.collect(toList());
+        }
+        try {
+            assertTrue(snapshots.size() <= 1,
+                "Too many snapshots matched for " + worldName);
+            return requireSnapshot(name, snapshots.stream().findAny().orElse(null));
+        } catch (Throwable t) {
+            Closer closer = Closer.create();
+            snapshots.forEach(closer::register);
+            throw closer.rethrowAndClose(t);
+        }
+    }
+
+    Snapshot requireSnapshot(String name, @Nullable Snapshot snapshot) throws IOException {
+        assertNotNull(snapshot, "No snapshot for " + name);
+        try {
+            assertEquals(name, snapshot.getInfo().getDisplayName());
+        } catch (Throwable t) {
+            Closer closer = Closer.create();
+            closer.register(snapshot);
+            throw closer.rethrowAndClose(t);
+        }
+        return snapshot;
+    }
+
+    ArchiveDir getRootOfArchive(Path archive) throws IOException {
+        return archiveNioSupport.tryOpenAsDir(archive)
+            .orElseThrow(() -> new AssertionError("No archive opener for " + archive));
+    }
+}

worldedit-core/src/test/java/com/sk89q/worldedit/world/snapshot/experimental/fs/FSSDTestType.java

@@ -0,0 +1,291 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.world.snapshot.experimental.fs;
+
+import com.google.common.collect.ImmutableList;
+import com.sk89q.worldedit.math.BlockVector3;
+import com.sk89q.worldedit.util.io.file.ArchiveDir;
+import com.sk89q.worldedit.world.DataException;
+import com.sk89q.worldedit.world.snapshot.experimental.Snapshot;
+import org.junit.jupiter.api.DynamicNode;
+import org.junit.jupiter.api.DynamicTest;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URI;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.FileTime;
+import java.time.ZonedDateTime;
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.stream.Stream;
+
+import static com.sk89q.worldedit.world.snapshot.experimental.fs.FileSystemSnapshotDatabaseTest.CHUNK_POS;
+import static com.sk89q.worldedit.world.snapshot.experimental.fs.FileSystemSnapshotDatabaseTest.CHUNK_TAG;
+import static com.sk89q.worldedit.world.snapshot.experimental.fs.FileSystemSnapshotDatabaseTest.TIME_ONE;
+import static com.sk89q.worldedit.world.snapshot.experimental.fs.FileSystemSnapshotDatabaseTest.TIME_TWO;
+import static com.sk89q.worldedit.world.snapshot.experimental.fs.FileSystemSnapshotDatabaseTest.WORLD_ALPHA;
+import static com.sk89q.worldedit.world.snapshot.experimental.fs.FileSystemSnapshotDatabaseTest.WORLD_BETA;
+import static java.util.stream.Collectors.toList;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.DynamicContainer.dynamicContainer;
+import static org.junit.jupiter.api.DynamicTest.dynamicTest;
+
+enum FSSDTestType {
+    EMPTY {
+        @Override
+        List<DynamicTest> getTests(FSSDContext context) {
+            return ImmutableList.of(
+                dynamicTest("return an empty stream from getSnapshots(worldName)",
+                    () -> context.db.getSnapshots(WORLD_ALPHA)),
+                dynamicTest("return an empty optional from getSnapshot(name)",
+                    () -> context.db.getSnapshot(context.nameUri(WORLD_ALPHA)))
+            );
+        }
+    },
+    WORLD_ONLY_DIR {
+        @Override
+        List<DynamicTest> getTests(FSSDContext context) throws IOException {
+            Path worldFolder = EntryMaker.WORLD_DIR.createEntry(context.db.getRoot(), WORLD_ALPHA);
+            Files.setLastModifiedTime(worldFolder, FileTime.from(TIME_ONE.toInstant()));
+            return singleSnapTest(context, WORLD_ALPHA, TIME_ONE);
+        }
+    },
+    WORLD_ONLY_DIM_DIR {
+        @Override
+        List<DynamicTest> getTests(FSSDContext context) throws IOException {
+            int dim = ThreadLocalRandom.current().nextInt();
+            Path worldFolder = EntryMaker.WORLD_DIM_DIR
+                .createEntry(context.db.getRoot(), new EntryMaker.DimInfo(WORLD_ALPHA, dim));
+            Files.setLastModifiedTime(worldFolder, FileTime.from(TIME_ONE.toInstant()));
+            return singleSnapTest(context, WORLD_ALPHA, TIME_ONE);
+        }
+    },
+    WORLD_ONLY_NO_REGION_DIR {
+        @Override
+        List<DynamicTest> getTests(FSSDContext context) throws IOException {
+            Path worldFolder = EntryMaker.WORLD_NO_REGION_DIR
+                .createEntry(context.db.getRoot(), WORLD_ALPHA);
+            Files.setLastModifiedTime(worldFolder, FileTime.from(TIME_ONE.toInstant()));
+            return singleSnapTest(context, WORLD_ALPHA, TIME_ONE);
+        }
+    },
+    WORLD_LEGACY_DIR {
+        @Override
+        List<DynamicTest> getTests(FSSDContext context) throws IOException {
+            Path worldFolder = EntryMaker.WORLD_LEGACY_DIR
+                .createEntry(context.db.getRoot(), WORLD_ALPHA);
+            Files.setLastModifiedTime(worldFolder, FileTime.from(TIME_ONE.toInstant()));
+            return singleSnapTest(context, WORLD_ALPHA, TIME_ONE);
+        }
+    },
+    WORLD_ONLY_ARCHIVE {
+        @Override
+        List<DynamicTest> getTests(FSSDContext context) throws IOException {
+            Path worldArchive = EntryMaker.WORLD_ARCHIVE
+                .createEntry(context.db.getRoot(), WORLD_ALPHA);
+            try (ArchiveDir rootOfArchive = context.getRootOfArchive(worldArchive)) {
+                Files.setLastModifiedTime(
+                    rootOfArchive.getPath(),
+                    FileTime.from(TIME_ONE.toInstant())
+                );
+            }
+            return singleSnapTest(context, WORLD_ALPHA + ".zip", TIME_ONE);
+        }
+    },
+    TIMESTAMPED_DIR {
+        @Override
+        List<? extends DynamicNode> getTests(FSSDContext context) throws IOException {
+            Path root = context.db.getRoot();
+            Path timestampedDir = EntryMaker.TIMESTAMPED_DIR
+                .createEntry(root, TIME_ONE);
+            EntryMaker.WORLD_DIR.createEntry(timestampedDir, WORLD_ALPHA);
+            EntryMaker.WORLD_ARCHIVE.createEntry(timestampedDir, WORLD_BETA);
+            return ImmutableList.of(
+                dynamicContainer("world dir",
+                    singleSnapTest(context,
+                        root.relativize(timestampedDir) + File.separator + WORLD_ALPHA,
+                        TIME_ONE)
+                ),
+                dynamicContainer("world archive",
+                    singleSnapTest(context,
+                        root.relativize(timestampedDir) + File.separator + WORLD_BETA + ".zip",
+                        TIME_ONE)
+                )
+            );
+        }
+    },
+    TIMESTAMPED_ARCHIVE {
+        @Override
+        List<? extends DynamicNode> getTests(FSSDContext context) throws IOException {
+            Path root = context.db.getRoot();
+            Path timestampedArchive = EntryMaker.TIMESTAMPED_ARCHIVE
+                .createEntry(root, TIME_ONE);
+            try (ArchiveDir timestampedDir = context.getRootOfArchive(timestampedArchive)) {
+                EntryMaker.WORLD_DIR.createEntry(timestampedDir.getPath(), WORLD_ALPHA);
+                EntryMaker.WORLD_ARCHIVE.createEntry(timestampedDir.getPath(), WORLD_BETA);
+            }
+            return ImmutableList.of(
+                dynamicContainer("world dir",
+                    singleSnapTest(context,
+                        root.relativize(timestampedArchive) + File.separator + WORLD_ALPHA,
+                        TIME_ONE)
+                )
+            );
+        }
+    },
+    WORLD_DIR_TIMESTAMPED_DIR {
+        @Override
+        List<? extends DynamicNode> getTests(FSSDContext context) throws IOException {
+            Path root = context.db.getRoot();
+            Path timestampedDirA = EntryMaker.TIMESTAMPED_DIR
+                .createEntry(root.resolve(WORLD_ALPHA), TIME_ONE);
+            Path timestampedDirB = EntryMaker.TIMESTAMPED_DIR
+                .createEntry(root.resolve(WORLD_BETA), TIME_ONE);
+            EntryMaker.WORLD_DIR.createEntry(timestampedDirA, WORLD_ALPHA);
+            EntryMaker.WORLD_ARCHIVE.createEntry(timestampedDirB, WORLD_BETA);
+            return ImmutableList.of(
+                dynamicContainer("world dir",
+                    singleSnapTest(context,
+                        root.relativize(timestampedDirA) + File.separator + WORLD_ALPHA,
+                        TIME_ONE)
+                ),
+                dynamicContainer("world archive",
+                    singleSnapTest(context,
+                        root.relativize(timestampedDirB) + File.separator + WORLD_BETA + ".zip",
+                        TIME_ONE)
+                )
+            );
+        }
+    },
+    TWO_TIMESTAMPED_WORLD_DIR {
+        @Override
+        List<DynamicTest> getTests(FSSDContext context) throws IOException {
+            Path root = context.db.getRoot();
+            Path timestampedDirA = EntryMaker.TIMESTAMPED_DIR
+                .createEntry(root, TIME_ONE);
+            EntryMaker.WORLD_DIR.createEntry(timestampedDirA, WORLD_ALPHA);
+            Path timestampedDirB = EntryMaker.TIMESTAMPED_DIR
+                .createEntry(root, TIME_TWO);
+            EntryMaker.WORLD_DIR.createEntry(timestampedDirB, WORLD_ALPHA);
+            return ImmutableList.of(
+                dynamicTest("list both snapshots in order (newest first)", () -> {
+                    List<Snapshot> snapshots = context.db
+                        .getSnapshotsNewestFirst(WORLD_ALPHA).collect(toList());
+                    assertEquals(2, snapshots.size());
+                    assertValidSnapshot(TIME_ONE, snapshots.get(0));
+                    assertValidSnapshot(TIME_TWO, snapshots.get(1));
+                }),
+                dynamicTest("list both snapshots in order (oldest first)", () -> {
+                    List<Snapshot> snapshots = context.db
+                        .getSnapshotsOldestFirst(WORLD_ALPHA).collect(toList());
+                    assertEquals(2, snapshots.size());
+                    assertValidSnapshot(TIME_TWO, snapshots.get(0));
+                    assertValidSnapshot(TIME_ONE, snapshots.get(1));
+                }),
+                dynamicTest("list only 1 if getting AFTER 2", () -> {
+                    List<Snapshot> snapshots = context.db
+                        .getSnapshotsAfter(WORLD_ALPHA, TIME_TWO).collect(toList());
+                    assertEquals(1, snapshots.size());
+                    assertValidSnapshot(TIME_ONE, snapshots.get(0));
+                }),
+                dynamicTest("list only 2 if getting BEFORE 1", () -> {
+                    List<Snapshot> snapshots = context.db
+                        .getSnapshotsBefore(WORLD_ALPHA, TIME_ONE).collect(toList());
+                    assertEquals(1, snapshots.size());
+                    assertValidSnapshot(TIME_TWO, snapshots.get(0));
+                }),
+                dynamicTest("list both if AFTER time before 2", () -> {
+                    List<Snapshot> snapshots = context.db
+                        .getSnapshotsAfter(WORLD_ALPHA, TIME_TWO.minusSeconds(1))
+                        .collect(toList());
+                    assertEquals(2, snapshots.size());
+                    // sorted newest first
+                    assertValidSnapshot(TIME_ONE, snapshots.get(0));
+                    assertValidSnapshot(TIME_TWO, snapshots.get(1));
+                }),
+                dynamicTest("list both if BEFORE time after 1", () -> {
+                        List<Snapshot> snapshots = context.db
+                            .getSnapshotsBefore(WORLD_ALPHA, TIME_ONE.plusSeconds(1))
+                            .collect(toList());
+                        assertEquals(2, snapshots.size());
+                        // sorted oldest first
+                        assertValidSnapshot(TIME_TWO, snapshots.get(0));
+                        assertValidSnapshot(TIME_ONE, snapshots.get(1));
+                    }
+                )
+            );
+        }
+    },
+    TWO_WORLD_ONLY_DIR {
+        @Override
+        List<? extends DynamicNode> getTests(FSSDContext context) throws IOException {
+            Path worldFolderA = EntryMaker.WORLD_DIR
+                .createEntry(context.db.getRoot(), WORLD_ALPHA);
+            Files.setLastModifiedTime(worldFolderA, FileTime.from(TIME_ONE.toInstant()));
+            Path worldFolderB = EntryMaker.WORLD_DIR
+                .createEntry(context.db.getRoot(), WORLD_BETA);
+            Files.setLastModifiedTime(worldFolderB, FileTime.from(TIME_TWO.toInstant()));
+            return Stream.of(
+                singleSnapTest(context, WORLD_ALPHA, TIME_ONE),
+                singleSnapTest(context, WORLD_BETA, TIME_TWO)
+            ).flatMap(List::stream).collect(toList());
+        }
+    };
+
+    List<DynamicTest> singleSnapTest(FSSDContext context, String name,
+                                                    ZonedDateTime time) {
+        return ImmutableList.of(
+            dynamicTest("return a valid snapshot for " + name, () -> {
+                try (Snapshot snapshot = context.requireSnapshot(name)) {
+                    assertValidSnapshot(time, snapshot);
+                }
+            }),
+            dynamicTest("list a valid snapshot for " + name, () -> {
+                try (Snapshot snapshot = context.requireListsSnapshot(name)) {
+                    assertValidSnapshot(time, snapshot);
+                }
+            })
+        );
+    }
+
+    private static void assertValidSnapshot(ZonedDateTime time,
+                                            Snapshot snapshot) throws IOException, DataException {
+        assertEquals(time, snapshot.getInfo().getDateTime());
+        // MCA file
+        assertEquals(CHUNK_TAG.toString(), snapshot.getChunkTag(CHUNK_POS).toString());
+        // MCR file
+        BlockVector3 offsetChunkPos = CHUNK_POS.add(32, 0, 32);
+        assertEquals(CHUNK_TAG.toString(), snapshot.getChunkTag(offsetChunkPos).toString());
+    }
+
+    abstract List<? extends DynamicNode> getTests(FSSDContext context) throws IOException;
+
+    Stream<DynamicNode> getNamedTests(FSSDContext context) throws IOException {
+        return Stream.of(dynamicContainer(
+            name(),
+            URI.create("method:" + getClass().getName() +
+                "#getTests(" + FSSDContext.class.getName() + ")"),
+            getTests(context).stream()
+        ));
+    }
+
+}

worldedit-core/src/test/java/com/sk89q/worldedit/world/snapshot/experimental/fs/FileSystemSnapshotDatabaseTest.java

@@ -0,0 +1,195 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.world.snapshot.experimental.fs;
+
+import com.google.common.io.ByteStreams;
+import com.google.common.io.Resources;
+import com.sk89q.jnbt.CompoundTag;
+import com.sk89q.worldedit.math.BlockVector2;
+import com.sk89q.worldedit.math.BlockVector3;
+import com.sk89q.worldedit.util.io.file.ArchiveNioSupport;
+import com.sk89q.worldedit.util.io.file.ArchiveNioSupports;
+import com.sk89q.worldedit.util.io.file.TrueVfsArchiveNioSupport;
+import com.sk89q.worldedit.util.io.file.ZipArchiveNioSupport;
+import com.sk89q.worldedit.world.DataException;
+import com.sk89q.worldedit.world.storage.ChunkStoreHelper;
+import com.sk89q.worldedit.world.storage.McRegionReader;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.DynamicNode;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestFactory;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.UncheckedIOException;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.function.Function;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+import java.util.zip.GZIPInputStream;
+import java.util.zip.GZIPOutputStream;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.DynamicContainer.dynamicContainer;
+
+@DisplayName("A FS Snapshot Database")
+class FileSystemSnapshotDatabaseTest {
+
+    static byte[] REGION_DATA;
+    static byte[] CHUNK_DATA;
+    static CompoundTag CHUNK_TAG;
+    static BlockVector3 CHUNK_POS;
+    static final String WORLD_ALPHA = "World Alpha";
+    static final String WORLD_BETA = "World Beta";
+
+    static final DateTimeFormatter FORMATTER =
+        DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH_mm_ss");
+    static final ZonedDateTime TIME_ONE = Instant.parse("2018-01-01T12:00:00.00Z")
+        .atZone(ZoneId.systemDefault());
+    static final ZonedDateTime TIME_TWO = TIME_ONE.minusDays(1);
+
+    private static Path TEMP_DIR;
+
+    @BeforeAll
+    static void setUpStatic() throws IOException, DataException {
+        try (InputStream in = Resources.getResource("world_region.mca.gzip").openStream();
+             GZIPInputStream gzIn = new GZIPInputStream(in)) {
+            REGION_DATA = ByteStreams.toByteArray(gzIn);
+        }
+        McRegionReader reader = new McRegionReader(new ByteArrayInputStream(REGION_DATA));
+        try {
+            // Find the single chunk
+            BlockVector2 chunkPos = IntStream.range(0, 32).mapToObj(
+                x -> IntStream.range(0, 32).filter(z -> reader.hasChunk(x, z))
+                    .mapToObj(z -> BlockVector2.at(x, z))
+            ).flatMap(Function.identity())
+                .findAny()
+                .orElseThrow(() -> new AssertionError("No chunk in region file."));
+            ByteArrayOutputStream cap = new ByteArrayOutputStream();
+            try (InputStream in = reader.getChunkInputStream(chunkPos);
+                 GZIPOutputStream gzOut = new GZIPOutputStream(cap)) {
+                ByteStreams.copy(in, gzOut);
+            }
+            CHUNK_DATA = cap.toByteArray();
+            CHUNK_TAG = ChunkStoreHelper.readCompoundTag(() -> new GZIPInputStream(
+                new ByteArrayInputStream(CHUNK_DATA)
+            ));
+            CHUNK_POS = chunkPos.toBlockVector3();
+        } finally {
+            reader.close();
+        }
+
+        TEMP_DIR = Files.createTempDirectory("worldedit-fs-snap-dbs");
+    }
+
+    @AfterAll
+    static void afterAll() throws IOException {
+        deleteTree(TEMP_DIR);
+    }
+
+    private static Path newTempDb() throws IOException {
+        return Files.createTempDirectory(TEMP_DIR, "db");
+    }
+
+    private static void deleteTree(Path root) throws IOException {
+        Files.walkFileTree(root, new SimpleFileVisitor<Path>() {
+            @Override
+            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
+                Files.deleteIfExists(file);
+                return FileVisitResult.CONTINUE;
+            }
+
+            @Override
+            public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
+                Files.deleteIfExists(dir);
+                return FileVisitResult.CONTINUE;
+            }
+        });
+    }
+
+    @DisplayName("makes the root directory absolute if needed")
+    @Test
+    void rootIsAbsoluteDir() throws IOException {
+        Path root = newTempDb();
+        try {
+            Path relative = root.getFileSystem().getPath("relative");
+            Files.createDirectories(relative);
+            FileSystemSnapshotDatabase db2 = new FileSystemSnapshotDatabase(relative,
+                ArchiveNioSupports.combined());
+            assertEquals(root.getFileSystem().getPath(".").toRealPath()
+                .resolve(relative), db2.getRoot());
+            Path absolute = root.resolve("absolute");
+            Files.createDirectories(absolute);
+            FileSystemSnapshotDatabase db3 = new FileSystemSnapshotDatabase(absolute,
+                ArchiveNioSupports.combined());
+            assertEquals(absolute, db3.getRoot());
+        } finally {
+            deleteTree(root);
+        }
+    }
+
+    @DisplayName("with a specific NIO support:")
+    @TestFactory
+    Stream<DynamicNode> withSpecificNioSupport() {
+        return Stream.of(
+            ZipArchiveNioSupport.getInstance(), TrueVfsArchiveNioSupport.getInstance()
+        )
+            .map(nioSupport -> {
+                Stream<? extends DynamicNode> nodes = Stream.of(FSSDTestType.values())
+                    .flatMap(type -> {
+                        try {
+                            return getTests(nioSupport, type);
+                        } catch (IOException e) {
+                            throw new UncheckedIOException(e);
+                        }
+                    });
+                return dynamicContainer(
+                    nioSupport.getClass().getSimpleName() + ", can, for format:",
+                    nodes
+                );
+            });
+    }
+
+    private static Stream<? extends DynamicNode> getTests(ArchiveNioSupport nioSupport,
+                                                          FSSDTestType type) throws IOException {
+        Path root = newTempDb();
+        try {
+            Path dbRoot = root.resolve("snapshots");
+            Files.createDirectories(dbRoot);
+            return type.getNamedTests(new FSSDContext(nioSupport, dbRoot));
+        } catch (Throwable t) {
+            deleteTree(root);
+            throw t;
+        }
+    }
+
+}