Not able to mock Laravel Model method

I am currently writing a test to test a model method.

My model Store has this method:

public function hourTemplate() {
    return $this->belongsTo(HourTemplate::class);
}

I have a test as well with this code in setUp method:

public function setUp() : void
    {
        parent::setUp();

        $this->storeMock = Mockery::mock(StoreModel::class)->makePartial();
        app()->instance(StoreModel::class, $this->storeMock);
    }

And test method is like this:

    public function test_getStoreHoursArray_when_hour_isNull() {
        $this->storeMock->shouldReceive('hourTemplate')->andReturn(new HourTemplate());

        dump((new StoreModel())->hourTemplate);

    }

But the returned value is null.