Is it possible to create a mock object with disabled constructor and manually setted protected properties?
Here is an idiotic example:
class A {
You can make the property public by using Reflection, and then set the desired value:
$a = new A;
$reflection = new ReflectionClass($a);
$reflection_property = $reflection->getProperty('p');
$reflection_property->setAccessible(true);
$reflection_property->setValue($a, 2);
Anyway in your example you don't need to set p value for the Exception to be raised. You are using a mock for being able to take control over the object behaviour, without taking into account it's internals.
So, instead of setting p = 2 so an Exception is raised, you configure the mock to raise an Exception when the blah method is called:
$mockA = $this->getMockBuilder('A')
->disableOriginalConstructor()
->getMock();
$mockA->expects($this->any())
->method('blah')
->will($this->throwException(new Exception));
Last, it's strange that you're mocking the A class in the ATest. You usually mock the dependencies needed by the object you're testing.
Hope this helps.