Move codec tests into dedicated folder

.github/workflows/ci.yml

@@ -46,12 +46,24 @@ jobs:
       - name: Install uv
         uses: astral-sh/setup-uv@v6
 
+      - name: Cache testdata
+        id: cache-testdata
+        uses: actions/cache@v4
+        with:
+          path: testdata/l4_sample
+          key: testdata-l4_sample-v1
+
       - name: Download testdata
+        if: steps.cache-testdata.outputs.cache-hit != 'true'
         run: |
-          mkdir testoutput
-          curl https://static.webknossos.org/data/zarr_v3/l4_sample.zip -o testdata/l4_sample.zip
+          curl -fL --retry 5 --retry-delay 10 --retry-all-errors \
+            https://static.webknossos.org/data/zarr_v3/l4_sample.zip -o testdata/l4_sample.zip
           cd testdata
-          unzip l4_sample.zip
+          unzip -q l4_sample.zip
+          rm l4_sample.zip
+
+      - name: Create testoutput
+        run: mkdir -p testoutput
 
       - name: Build
         run: mvn compile

src/test/java/dev/zarr/zarrjava/ZarrTest.java

@@ -1,7 +1,11 @@
 package dev.zarr.zarrjava;
 
 import dev.zarr.zarrjava.core.Attributes;
+import dev.zarr.zarrjava.store.StoreHandle;
+import dev.zarr.zarrjava.v3.Array;
+import dev.zarr.zarrjava.v3.ArrayMetadataBuilder;
 import dev.zarr.zarrjava.v3.DataType;
+import dev.zarr.zarrjava.v3.codec.CodecBuilder;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeAll;
 
@@ -12,8 +16,11 @@
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
+import java.util.function.Function;
 import java.util.stream.Stream;
 
+import static dev.zarr.zarrjava.utils.Utils.toLongArray;
+
 public class ZarrTest {
 
     public static final Path TESTDATA = Paths.get("testdata");
@@ -231,5 +238,38 @@ protected void assertIsTestdata(ucar.ma2.Array result, dev.zarr.zarrjava.core.Da
         }
     }
 
+    /**
+     * Writes {@link #testdata(dev.zarr.zarrjava.core.DataType)} through the given codec pipeline,
+     * reopens the array from the store and asserts the data round-trips unchanged.
+     * Uses the array's default chunk shape.
+     */
+    protected void assertCodecRoundtrip(StoreHandle storeHandle, DataType dataType,
+            Function<CodecBuilder, CodecBuilder> codecs) throws ZarrException, IOException {
+        assertCodecRoundtrip(storeHandle, dataType, null, codecs);
+    }
+
+    /**
+     * Writes {@link #testdata(dev.zarr.zarrjava.core.DataType)} through the given codec pipeline,
+     * reopens the array from the store and asserts the data round-trips unchanged.
+     *
+     * @param chunkShape chunk shape to use, or {@code null} for the default chunk shape
+     */
+    protected void assertCodecRoundtrip(StoreHandle storeHandle, DataType dataType, int[] chunkShape,
+            Function<CodecBuilder, CodecBuilder> codecs) throws ZarrException, IOException {
+        ucar.ma2.Array testData = testdata(dataType);
+        ArrayMetadataBuilder builder = Array.metadataBuilder()
+                .withShape(toLongArray(testData.getShape()))
+                .withDataType(dataType)
+                .withCodecs(codecs);
+        if (chunkShape != null) {
+            builder = builder.withChunkShape(chunkShape);
+        }
+        Array array = Array.create(storeHandle, builder.build());
+        array.write(testData);
+
+        Array reopenedArray = Array.open(storeHandle);
+        assertIsTestdata(reopenedArray.read(), dataType);
+    }
+
 
 }