gistfile1.txt

class ExampleTest extends BaseTestCase
{
    public function testA()
    {
        $contact1 = new Contact();
        $contact2 = new Contact();

        $this->prophesize();

        $mockB = $this->prophesize(B::class);
        $mockB->doStuff($contact2)->shouldBeCalled();

        $instanceA = new A($mockB->reveal());
        $instanceA->doStuff($contact1);
    }
}
class A
{
    /**
     * @var B
     */
    private $classB;

    public function __construct(B $classB)
    {
        $this->classB = $classB;
    }

    public function doStuff(Contact $contact)
    {
        $this->classB->doStuff($contact);
    }

}
class B
{
    public function doStuff(Contact $contact)
    {

    }
}