@Test
public void testSave_ToFile() throws IOException {

    File file = new File(outPath("testToFile.csv"));
    DataFrame df = DataFrame.newFrame("A", "B").foldByRow(
            1, 2,
            3, 4);
    Csv.saver().save(df, file);
    assertEquals("A,B\r\n" +
            "1,2\r\n" +
            "3,4\r\n", readFile(file.getAbsolutePath()));
}