test: Shard test updates

* test a list of nulls is returned for non-existing blocks
* test number of backend read calls for readBlocks

Author: bogovicj

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

@@ -322,6 +322,19 @@ public void writeShardDataSizeTest() {
 			data[i] = (byte)((100) + (10) + i);
 		}
 
+		/*
+		 * No blocks or shards exist.
+		 * Calling readBlocks should return a list that is the same length as the requested grid positions,
+		 * and every entry should be null.
+		 */
+		final long[][] newBlockIndices = new long[][]{{0, 0}, {1, 1}, {0, 4}, {0, 5}, {10, 10}};
+		final List<DataBlock<Object>> readBlocks = writer.readBlocks(dataset, datasetAttributes, Arrays.asList(newBlockIndices));
+		assertEquals(newBlockIndices.length, readBlocks.size());
+		assertTrue("readBlocks for empty shard: all blocks null", readBlocks.stream().allMatch(blk -> blk == null));
+
+		/*
+		 * Now write blocks
+		 */
 		writer.writeBlocks(
 				dataset,
 				datasetAttributes,
@@ -367,20 +380,6 @@ public void writeShardDataSizeTest() {
 
 	}
 
-	@Test
-	public void readBlocksTest() {
-
-		final N5Writer n5 = tempN5Factory.createTempN5Writer();
-		final DatasetAttributes datasetAttributes = getTestAttributes(
-				new long[]{24, 24},
-				new int[]{8, 8},
-				new int[]{2, 2});
-
-		final String dataset = "writeReadBlocks";
-		final long[][] newBlockIndices = new long[][]{{0, 0}, {1, 1}, {0, 4}, {0, 5}, {10, 10}};
-		final List<DataBlock<Object>> readBlocks = n5.readBlocks(dataset, datasetAttributes, Arrays.asList(newBlockIndices));
-	}
-
 	@Test
 	public void writeReadBlockTest() {
 
@@ -484,69 +483,6 @@ public void writeReadShardTest() {
 		}
 	}
 
-	private int[] range(int N) {
-		return IntStream.range(0, N).toArray();
-	}
-
-	/**
-	 * Checks how many read calls to the backend are performed for a particular readBlocks
-	 * call. At this time (Nov 4 2025), one read for the index, and one read per block are performed.
-	 */
-	public void numReadsTest() {
-
-		final TrackingN5Writer writer = (TrackingN5Writer)tempN5Factory.createTempN5Writer();
-
-		final DatasetAttributes datasetAttributes = getTestAttributes(
-				new long[]{24, 24},
-				new int[]{8, 8},
-				new int[]{2, 2}
-		);
-
-		final String dataset = "writeReadBlocks";
-		writer.remove(dataset);
-		writer.createDataset(dataset, datasetAttributes);
-
-		final int[] blockSize = datasetAttributes.getBlockSize();
-		final int numElements = blockSize[0] * blockSize[1];
-
-		final byte[] data = new byte[numElements];
-		for (int i = 0; i < data.length; i++) {
-			data[i] = (byte)((100) + (10) + i);
-		}
-
-		writer.writeBlocks(
-				dataset,
-				datasetAttributes,
-				/* shard (0, 0) */
-				new ByteArrayDataBlock(blockSize, new long[]{0, 0}, data),
-				new ByteArrayDataBlock(blockSize, new long[]{0, 1}, data),
-				new ByteArrayDataBlock(blockSize, new long[]{1, 0}, data),
-				new ByteArrayDataBlock(blockSize, new long[]{1, 1}, data),
-
-				/* shard (1, 0) */
-				new ByteArrayDataBlock(blockSize, new long[]{4, 0}, data),
-				new ByteArrayDataBlock(blockSize, new long[]{5, 0}, data),
-
-				/* shard (2, 2) */
-				new ByteArrayDataBlock(blockSize, new long[]{11, 11}, data)
-		);
-
-		writer.resetNumMaterializeCalls();
-		writer.readBlocks(dataset, datasetAttributes, Collections.singletonList(new long[] {0,0}));
-		System.out.println(writer.getNumMaterializeCalls());
-
-		ArrayList ptList = new ArrayList<>();
-		ptList.add(new long[] {0,0});
-		ptList.add(new long[] {0,1});
-		ptList.add(new long[] {1,0});
-		ptList.add(new long[] {1,1});
-
-		writer.resetNumMaterializeCalls();
-		writer.readBlocks(dataset, datasetAttributes, ptList);
-		System.out.println(writer.getNumMaterializeCalls());
-		System.out.println("");
-	}
-
     @Test
     public void shardExistsTest() {
 
@@ -603,6 +539,68 @@ public void shardExistsTest() {
         Assert.assertFalse("Shard (0,2) should not exist", assertShardExistsTracking.apply(new long[]{0, 2}));
     }
 
+	/**
+	 * Checks how many read calls to the backend are performed for a particular readBlocks
+	 * call. At this time (Jan 4 2026), one read for the index, and one read per block are performed.
+	 */
+	@Test
+	public void testPartialReadAggregationBehavior() {
+
+        final DatasetAttributes datasetAttributes = getTestAttributes(
+                new long[]{24, 24},
+                new int[]{8, 8},
+                new int[]{2, 2}
+        );
+
+		try (TrackingN5Writer writer = (TrackingN5Writer)tempN5Factory.createTempN5Writer()) {
+
+	        final String dataset = "shardExists";
+	        writer.remove(dataset);
+	        DatasetAttributes attrs = writer.createDataset(dataset, datasetAttributes);
+
+	        final int[] blockSize = attrs.getBlockSize();
+	        final int numElements = blockSize[0] * blockSize[1];
+
+	        final byte[] data = new byte[numElements];
+	        for (int i = 0; i < data.length; i++) {
+	            data[i] = (byte)(i);
+	        }
+
+			// four blocks in shard (0,0)
+			ArrayList<long[]> ptList = new ArrayList<>();
+			ptList.add(new long[] {0,0});
+			ptList.add(new long[] {0,1});
+			ptList.add(new long[] {1,0});
+			ptList.add(new long[] {1,1});
+
+	        /* write blocks to shard (0,0) */
+			writer.writeBlocks(
+					dataset,
+					datasetAttributes,
+					new ByteArrayDataBlock(blockSize, ptList.get(0), data),
+					new ByteArrayDataBlock(blockSize, ptList.get(1), data),
+					new ByteArrayDataBlock(blockSize, ptList.get(2), data),
+					new ByteArrayDataBlock(blockSize, ptList.get(3), data)
+			);
+
+			writer.resetNumMaterializeCalls();
+			writer.readBlocks(dataset, datasetAttributes, ptList);
+
+			// TODO change this if and when we implement aggregation of read calls
+			// one for the index, one for each of the four blocks
+			assertEquals(5, writer.getNumMaterializeCalls());
+
+			writer.resetNumMaterializeCalls();
+			writer.readShard(dataset, datasetAttributes, new long[] {0,0});
+			// one for the index, one for each of the four blocks
+			assertEquals(5, writer.getNumMaterializeCalls());
+		}
+	}
+
+	private int[] range(int N) {
+		return IntStream.range(0, N).toArray();
+	}
+
     /**
      * An N5Writer that tracks the number of materialize calls performed by
      * its underlying key value access.