@Test
public void outputTest() {

    List<Map<String, Object>> stuff = ImmutableList.of(
            ImmutableMap.of("a", "1", "b", 2),
            ImmutableMap.of("b", 2, "c", 3, "d", 4),
            ImmutableMap.of("a", ImmutableList.of(1, 2, 3)));
    ByteArrayOutputStream out = new ByteArrayOutputStream();
    PrintStream stream = new PrintStream(out);
    Exporters.csv(stream).export(stuff);
    StringBuilder expected = new StringBuilder();
    expected.append("a,b,c,d").append(System.lineSeparator())
            .append("1,2,null,null").append(System.lineSeparator())
            .append("null,2,3,4").append(System.lineSeparator())
            .append("\"1,2,3\",null,null,null");
    Assert.assertEquals(expected.toString(), out.toString());
}