String separator = LINE_SEPARATOR.value();
    assertEquals("foo" + separator + "bar" + separator + "baz" + separator, sink.getString());
  }

  public void testWriteLines_stream_separator() throws IOException {
    sink.writeLines(ImmutableList.of("foo", "bar", "baz").stream(), "!");
    assertEquals("foo!bar!baz!", sink.getString());
  }