### Question:
DataSetUtils extends DataSetUtilsHelper { protected static double[] cropToLength(final double[] in, final int length) { if (in.length == length) { return in; } return Arrays.copyOf(in, length); } private  DataSetUtils(); static AbstractDataSet<?> copyDataSet(final DataSet ds); static double error(final DataSet dataSet, final ErrType eType, final double x); static double error(final DataSet dataSet, final ErrType eType, final int index); static double[] errors(final DataSet dataSet, final ErrType eType); static String getFileName(final DataSet dataSet, final String fileName); static String getISODate(final long timeMillis, final String format); static DataSet readDataSetFromByteArray(final byte[] byteArray); static DataSet readDataSetFromFile(final String fileName); static DataSet readDataSetFromFile(final String fileName, final Compression compression); static DataSet readDataSetFromStream(final SplitCharByteInputStream inputStream); static void setExportMetaDataByDefault(final boolean state); static void setUseFloat32BinaryStandard(final boolean state); static boolean useExportMetaDataByDefault(); static boolean useFloat32BinaryStandard(); static void writeDataSetToByteArray(final DataSet dataSet, final ByteArrayOutputStream byteOutput,
            final boolean binary, final boolean asFloat); static String writeDataSetToFile(final DataSet dataSet, final Path path, final String fileName); static String writeDataSetToFile(final DataSet dataSet, final Path path, final String fileName,
            final boolean binary); static String writeDataSetToFile(final DataSet dataSet, final Path path, final String fileName,
            final Compression compression); static String writeDataSetToFile(final DataSet dataSet, final Path path, final String fileName,
            final Compression compression, final boolean binary); static final String NO_DATASET; }### Answer:
@Test void testHelperFunctions() { final double[] array = new double[] { 1, 2, 3, 4 }; assertArrayEquals(new double[] { 1, 2, 3 }, DataSetUtils.cropToLength(array, 3)); assertSame(array, DataSetUtils.cropToLength(array, 4)); }