function test_get_differences_with_zero_query_results()
 {
     $s = 'http://example.com/subj';
     $result = new DataTableResult($this->_select_result_zero_results, $s);
     $dt = new DataTable("http://example.org/store");
     $dt->map('http://example.org/title', 'title');
     $dt->set('title', 'baz');
     $dt->where('_uri', $s);
     $diffs = $dt->get_differences($result);
     $this->assertEquals(1, count($diffs));
     $this->assertTrue(array_key_exists($s, $diffs));
     $this->assertEquals(0, count($diffs[$s]['removals']));
     $this->assertEquals(1, count($diffs[$s]['additions']));
 }