MATLAB: How to change property behavior for a mocked object

MATLABmockmocking frameworkooptest

I'm trying to use the mocking framework for unit tests
I'm trying to make the property of a mock object return another mock object, but the behavior object doesn't have the property
classdef MyClass
    properties (GetAccess=public, SetAccess=protected)
        prop1;
    end
    
    methods
        function this = answer()
        end
    end
end
this is the mock decleration:
testCase = matlab.mock.TestCase.forInteractiveUse;
[mock,behav] = testCase.createMock(?MyClass);
% this would obciously throw an exception because the property set method is protected
mock.prop1 = ""; 
    You cannot set the read-only property 'prop1' of MyClassMock.
% this throws an exception because the behavior object doesn't have this property
p = behav.prop1; 
    No appropriate method, property, or field 'prop1' for class 'matlab.mock.classes.MyClassBehavior'.
now i can't set the value of the mock object because the set access is protected
and i can't use the behavior object to change the property behavior because I can't find the propertyBehavior thing anywhere
I'm obviously missing something, but all the examples I've seen in the documentation show how to use a custom mock object with "AddedProperties"
and I could be tackling this the wrong way, but I prefer to create the mock object using the meta class

Best Answer

Mock objects are still a recent feature of MATLAB and I don't think they are practical for testing classes yet. There are still quite a few features that are lacking for sufficiantly replicating object behaviour, for instance having a mock object method call assign a value to a protected property.
The solution to the above case is to create your mock without using the meta-class instance:
testCase = matlab.mock.TestCase.forInteractiveUse;
[MyClassMock, behaviour] = createMock(testCase, 'AddedProperties', "prop1", 'AddedMethods', "answer")
testCase.assignOutputsWhen(get(behaviour.prop1), 'abc')
p = MyClassMock.prop1
It's not ideal but I don't think there's any other option at this time. You can still test for access violations this way:
import matlab.mock.actions.ThrowException
when(set(behaviour.prop1),...
    ThrowException(MException('MATLAB:class:SetProhibited',...
    'You cannot set the read-only property ''prop1'' of MyClass.')))
Creating a mock from a meta-class only works for classes with abstract properties and methods.
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