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single: Cookbook; Big Parent Class
Big Parent Class
================
In some application code, especially older legacy code, we can come across some
classes that extend a "big parent class" - a parent class that knows and does
too much:
.. code-block:: php
class BigParentClass
{
public function doesEverything()
{
// sets up database connections
// writes to log files
}
}
class ChildClass extends BigParentClass
{
public function doesOneThing()
{
// but calls on BigParentClass methods
$result = $this->doesEverything();
// does something with $result
return $result;
}
}
We want to test our ``ChildClass`` and its ``doesOneThing`` method, but the
problem is that it calls on ``BigParentClass::doesEverything()``. One way to
handle this would be to mock out **all** of the dependencies ``BigParentClass``
has and needs, and then finally actually test our ``doesOneThing`` method. It's
an awful lot of work to do that.
What we can do, is to do something... unconventional. We can create a runtime
partial test double of the ``ChildClass`` itself and mock only the parent's
``doesEverything()`` method:
.. code-block:: php
$childClass = \Mockery::mock('ChildClass')->makePartial();
$childClass->shouldReceive('doesEverything')
->andReturn('some result from parent');
$childClass->doesOneThing(); // string("some result from parent");
With this approach we mock out only the ``doesEverything()`` method, and all the
unmocked methods are called on the actual ``ChildClass`` instance.
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