test/fix: N5Writer in ShardTest tracks, does not serialize

* refactor ShardedN5Writer to TrackingN5Writer
* a special N5Writer class is not needed to
* rather, particular DatasetAttribute instances can be used to test
sharding

Author: bogovicj

src/test/java/org/janelia/saalfeldlab/n5/shard/ShardTest.java

@@ -39,11 +39,9 @@
 import org.janelia.saalfeldlab.n5.N5FSTest;
 import org.janelia.saalfeldlab.n5.N5KeyValueWriter;
 import org.janelia.saalfeldlab.n5.N5Writer;
-import org.janelia.saalfeldlab.n5.NameConfigAdapter;
 import org.janelia.saalfeldlab.n5.RawCompression;
 import org.janelia.saalfeldlab.n5.N5Exception.N5NoSuchKeyException;
 import org.janelia.saalfeldlab.n5.GsonKeyValueN5Writer;
-import org.janelia.saalfeldlab.n5.codec.CodecInfo;
 import org.janelia.saalfeldlab.n5.codec.DataCodecInfo;
 import org.janelia.saalfeldlab.n5.codec.N5BlockCodecInfo;
 import org.janelia.saalfeldlab.n5.codec.RawBlockCodecInfo;
@@ -55,9 +53,10 @@
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
 
-import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 
+import static org.junit.Assert.assertTrue;
+
 import java.io.File;
 import java.io.IOException;
 import java.io.UncheckedIOException;
@@ -88,15 +87,15 @@ public class ShardTest {
 		@Override public N5Writer createTempN5Writer() {
 
 			if (LOCAL_DEBUG) {
-				final N5Writer writer = new ShardedN5Writer("src/test/resources/test.n5");
+				final N5Writer writer = new TrackingN5Writer("src/test/resources/test.n5");
 				writer.remove(""); // Clear old when starting new test
 				return writer;
 			}
 
 			final String basePath = new File(tempN5PathName()).toURI().normalize().getPath();
 			try {
 				String uri = new URI("file", null, basePath, null).toString();
-				return new ShardedN5Writer(uri);
+				return new TrackingN5Writer(uri);
 			} catch (URISyntaxException e) {
 				e.printStackTrace();
 			}
@@ -117,10 +116,6 @@ private String tempN5PathName() {
 		}
 	};
 
-	public static GsonBuilder gsonBuilder() {
-		return new GsonBuilder();
-	}
-
 	@Parameterized.Parameters(name = "IndexLocation({0}), Index ByteOrder({1})")
 	public static Collection<Object[]> data() {
 
@@ -313,15 +308,17 @@ public void writeShardDataSizeTest() {
 
 		int numBlocksPerShard = 16;
 		final int n5HeaderSizeBytes = 12; // 2 + 2 + 4*2
-		final DatasetAttributes datasetAttributes = getTestAttributes(
+		final DatasetAttributes attrs = getTestAttributes(
 				new long[]{24, 24},
 				new int[]{8, 8},
 				new int[]{2, 2}
 		);
 
 		final String dataset = "writeBlocksShardSize";
 		writer.remove(dataset);
-		writer.createDataset(dataset, datasetAttributes);
+		final DatasetAttributes datasetAttributes = writer.createDataset(dataset, attrs);
+		assertTrue(datasetAttributes.isSharded());
+
 		final KeyValueAccess kva = ((N5KeyValueWriter)writer).getKeyValueAccess();
 
 		final int[] blockSize = datasetAttributes.getBlockSize();
@@ -438,7 +435,7 @@ public void writeReadBlockTest() {
 	 */
 	public void numReadsTest() {
 
-		final ShardedN5Writer writer = (ShardedN5Writer)tempN5Factory.createTempN5Writer();
+		final TrackingN5Writer writer = (TrackingN5Writer)tempN5Factory.createTempN5Writer();
 
 		final DatasetAttributes datasetAttributes = getTestAttributes(
 				new long[]{24, 24},
@@ -492,43 +489,23 @@ public void numReadsTest() {
 	}
 
 	/**
-	 * An N5Writer that serializing the sharding codecs, enabling testing of
-	 * shard functionality, despite the fact that the N5 format does not support
-	 * sharding.
+	 * An N5Writer that tracks the number of materialize calls performed by 
+	 * its underlying key value access.
 	 */
-	public static class ShardedN5Writer extends N5KeyValueWriter {
-
-		Gson gson;
-
-		public ShardedN5Writer(String basePath) {
+	public static class TrackingN5Writer extends N5KeyValueWriter {
+		public TrackingN5Writer(String basePath) {
 
 			super( new TrackingFileSystemKeyValueAccess(FileSystems.getDefault()),
 					basePath, new GsonBuilder(), false);
 		}
 
-		public ShardedN5Writer(String basePath, GsonBuilder gsonBuilder) {
-
-			this(basePath);
-			gsonBuilder.registerTypeAdapter(DataType.class, new DataType.JsonAdapter());
-			gsonBuilder.registerTypeHierarchyAdapter(CodecInfo.class, NameConfigAdapter.getJsonAdapter(CodecInfo.class));
-			gsonBuilder.registerTypeHierarchyAdapter(ByteOrder.class, RawBlockCodecInfo.byteOrderAdapter);
-			gsonBuilder.disableHtmlEscaping();
-			gson = gsonBuilder.create();
-		}
-
 		public void resetNumMaterializeCalls() {
 			((TrackingFileSystemKeyValueAccess)super.getKeyValueAccess()).numMaterializeCalls = 0;
 		}
 
 		public int getNumMaterializeCalls() {
 			return ((TrackingFileSystemKeyValueAccess)super.getKeyValueAccess()).numMaterializeCalls;
 		}
-
-		@Override
-		public Gson getGson() {
-			// the super constructor needs the gson instance, unfortunately
-			return gson == null ? super.gson : gson;
-		}
 	}
 
 	private static class TrackingFileSystemKeyValueAccess extends FileSystemKeyValueAccess {