Sokil\Mongo\Pipeline\ExpressionTest::testNormalize_ExpressionObject PHP Method

    public function testNormalize_ExpressionObject()
    {
        $subExpression = new Expression();
        $subExpression->mod('$field', 2);
        $expression = new Expression();
        $expression->add(array(1, function ($expression) {
            $expression->multiply('$field', 12);
        }, $subExpression));
        $this->assertEquals(array('$add' => array(1, array('$multiply' => array('$field', 12)), array('$mod' => array('$field', 2)))), Expression::normalize($expression));
    }