    @Test
    public void testExtractedInputForSingleTransformerWithColumnModification() {

        Transformer t = createTransformer(Arrays.asList("a", "b", "c"), Arrays.asList("a1", "b1", "c"));
        Set<String> inputs = PipelineUtils.extractRequiredInputColumns(new Transformer[] {t});
        assertEquals(inputs.size(), 3);
        assertTrue(inputs.containsAll(Arrays.asList("a","b","c")));
        assertFalse(inputs.contains("a1"));
        assertFalse(inputs.contains("b1"));
    }