add test

Signed-off-by: Max Lepikhin <[email protected]>

ml-algorithms/src/test/java/org/opensearch/ml/engine/utils/FileUtilsTest.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.ml.engine.utils;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Random;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+public class FileUtilsTest {
+    private final TemporaryFolder tempDir = new TemporaryFolder();
+
+    @Before
+    public void setUp() throws Exception {
+        tempDir.create();
+    }
+
+    @After
+    public void tearUp() {
+        tempDir.delete();
+    }
+
+    @Test
+    public void testSplitFileIntoChunks() throws Exception {
+        // Write file.
+        Random random = new Random();
+        File file = tempDir.newFile("large_file");
+        byte[] data = new byte[1017];
+        random.nextBytes(data);
+        Files.write(file.toPath(), data);
+
+        // Split file into chunks.
+        int chunkSize = 325;
+        List<String> chunkPaths = FileUtils
+                .splitFileIntoChunks(file, tempDir.newFolder().toPath(), chunkSize);
+
+        // Verify.
+        int currentPosition = 0;
+        for (String chunkPath : chunkPaths) {
+            byte[] chunk = Files.readAllBytes(Path.of(chunkPath));
+            assertTrue("Chunk size", currentPosition + chunk.length <= data.length);
+            Assert.assertArrayEquals(Arrays
+                    .copyOfRange(data, currentPosition, currentPosition + chunk.length), chunk);
+            currentPosition += chunk.length;
+        }
+        assertEquals(currentPosition, data.length);
+    }
+}