@Test
public void testToString() {

    DataFrameInlinePrintWorker w = new DataFrameInlinePrintWorker(new StringBuilder(), 5, 10);
    assertEquals("{col1:one,column2:1},{col1:two,column2:2},{col1:three,column2:3},{col1:four,column2:4}",
            w.print(df).toString());
}