@Test
public void testSave_NoMkdirs() {

    String path = outPath("NoMkdirs" + File.separator + "f4" + File.separator + "testToFile.csv");
    File file = new File(path);
    DataFrame df = DataFrame.newFrame("A", "B").foldByRow(
            1, 2,
            3, 4);
    assertThrows(RuntimeException.class, () -> Csv.saver().save(df, file));
}