模拟支持链接方法的对象

Question

I'm wondering if there's a fairly concise way of mocking objects which support chaining of methods... so for example, a database query object might have a method call that looks like this:

$result = $database->select('my_table')->where(array('my_field'=>'a_value'))->limit(1)->execute();

The problem comes if I have to mock two different select queries so that they return different results. Any ideas?

This is specifically about PHPUnit, but experiences from other unit testing frameworks will help.

Answer 1

I am not sure this is what you are looking for, so please leave a comment:

class StubTest extends PHPUnit_Framework_TestCase
{
    public function testChainingStub()
    {
        // Creating the stub with the methods to be called
        $stub = $this->getMock('Zend_Db_Select', array(
            'select', 'where', 'limit', 'execute'
        ), array(), '', FALSE);

        // telling the stub to return a certain result on execute
        $stub->expects($this->any())
             ->method('execute')
             ->will($this->returnValue('expected result'));

        // telling the stub to return itself on any other calls
        $stub->expects($this->any())
             ->method($this->anything())
             ->will($this->returnValue($stub));

        // testing that we can chain the stub
        $this->assertSame(
            'expected result',
            $stub->select('my_table')
                 ->where(array('my_field'=>'a_value'))
                 ->limit(1)
                 ->execute()
        );
    }
}

You can combine this with expectations:

class StubTest extends PHPUnit_Framework_TestCase
{
    public function testChainingStub()
    {
        // Creating the stub with the methods to be called
        $stub = $this->getMock('Zend_Db_Select', array(
            'select', 'where', 'limit', 'execute'
        ), array(), '', FALSE);

        // overwriting stub to return something when execute is called
        $stub->expects($this->exactly(1))
             ->method('execute')
             ->will($this->returnValue('expected result'));

        $stub->expects($this->exactly(1))
             ->method('limit')
             ->with($this->equalTo(1))
             ->will($this->returnValue($stub));

        $stub->expects($this->exactly(1))
             ->method('where')
             ->with($this->equalTo(array('my_field'=>'a_value')))
             ->will($this->returnValue($stub));

        $stub->expects($this->exactly(1))
             ->method('select')
             ->with($this->equalTo('my_table'))
             ->will($this->returnValue($stub));

        // testing that we can chain the stub
        $this->assertSame(
            'expected result',
            $stub->select('my_table')
                 ->where(array('my_field'=>'a_value'))
                 ->limit(1)
                 ->execute()
        );
    }
}