public function testMerge()
{
$expression1 = new Expression();
$expression1->where('a', 77);
$expression1->where('b', 88);
$expression1->whereGreater('c', 99);
$expression2 = new Expression();
$expression2->where('a', 55);
$expression1->whereLess('c', 66);
$expression1->merge($expression2);
$this->assertEquals(array('a' => array(77, 55), 'b' => 88, 'c' => array('$gt' => 99, '$lt' => 66)), $expression1->toArray());
}
