test.php

<?php
  App::uses('PwfSource', 'Model/Datasource');
  App::uses('Model', 'Model');
  
  public function setUp() {
        $this->Source = ClassRegistry::init('PwfSource');
        $this->sourceMethods = get_class_methods($this->Source);
        $methods = array_diff($this->sourceMethods, ['read', '__call', '__isset', '__get']);
        $this->Source = $this->getMock('PwfSource', $methods);

        $this->Model = $this->getMock('Model');

    }
     public function testRead() {
        $this->Source->expects($this->any())
            ->method('request')
            ->with(
                $this->anything(),
                $this->anything()
            )
            ->will($this->returnValue($expected_result));

        $result = $this->Source->read($this->Model, ['conditions' => array('id' => 9379)]);

        $this->assertEquals($expected_result, $result);
    }