Removing dependencies in constructor using PHPunit

While trying to get a legacy codebase under testing, I came across an object that does the following:

class Foo
{
    public function __construct($someargs)
    {
        $this->bar = new Bar();
        // [lots more code]
    }
}

      

        
        
        
      

    

The bar in this case has a constructor that does some Bad Things, for example. connection to the database. I'm trying to focus on trying out this Foo class so changed it to something like this:

class Foo
{
    public function __construct($someargs)
    {
        $this->bar = $this->getBarInstance();
        // [lots more code]
    }

    protected function getBarInstance()
    {
        return new Bar();
    }
}

      

        
        
        
      

    

And tried to test it with the following PHPUnit test:

class FooTest extends PHPUnit_Framework_TestCase
{
    public function testInstance()
    {

        $bar = $this->getMock('Bar');
        $foo = $this->getMock('Foo', array('getBarInstance'));
        $foo->expects($this->any())
            ->method('getBarInstance')
            ->will($this->returnValue($bar));

    }

}

      

        
        
        
      

    

However, that won't work - the Foo () constructor is called before my -> expects () is added, so the mocked getBarInstance () method returns zero.

Is there a way to disable this dependency without refactoring the way the constructors use the class?