### Question:
HashTransformer implements Transformer { @Override public OutputColumns getOutputColumns() { final StringJoiner joiner = new StringJoiner(", "); for (InputColumn<?> column : _columns) { joiner.add(column.getName()); } return new OutputColumns(String.class, "Hash of " + joiner.toString(), "Input length"); } HashTransformer();   HashTransformer(final InputColumn<?>[] columns, final Algorithm algorithm); @Override OutputColumns getOutputColumns(); @Override String[] transform(final InputRow inputRow);  }### Answer:
@Test public void testGetOutputColumns() throws Exception { final HashTransformer transformer = new HashTransformer(new InputColumn[] { _column }, HashTransformer.Algorithm.SHA_512); assertEquals(2, transformer.getOutputColumns().getColumnCount()); assertEquals(String.class, transformer.getOutputColumns().getColumnType(0)); assertEquals("Input length", transformer.getOutputColumns().getColumnName(1)); assertTrue(transformer.getOutputColumns().getColumnName(0).startsWith("Hash of")); }