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    single: Mocking; Object Recording

Mock Object Recording
=====================

In certain cases, you may find that you are testing against an already
established pattern of behaviour, perhaps during refactoring. Rather then hand
crafting mock object expectations for this behaviour, you could instead use
the existing source code to record the interactions a real object undergoes
onto a mock object as expectations - expectations you can then verify against
an alternative or refactored version of the source code.

To record expectations, you need a concrete instance of the class to be
mocked.  This can then be used to create a partial mock to which is given the
necessary code to execute the object interactions to be recorded. A simple
example is outline below (we use a closure for passing instructions to the
mock).

Here we have a very simple setup, a class (``SubjectUser``) which uses another
class (``Subject``) to retrieve some value. We want to record as expectations
on our mock (which will replace ``Subject`` later) all the calls and return
values of a Subject instance when interacting with ``SubjectUser``.

.. code-block:: php

    class Subject
    {

        public function execute() {
            return 'executed!';
        }

    }

    class SubjectUser
    {

        public function use(Subject $subject) {
            return $subject->execute();
        }

    }

Here's the test case showing the recording:

.. code-block:: php

    class SubjectUserTest extends PHPUnit_Framework_TestCase
    {

        public function tearDown()
        {
            \Mockery::close();
        }

        public function testSomething()
        {
            $mock = \Mockery::mock(new Subject);
            $mock->shouldExpect(function ($subject) {
                $user = new SubjectUser;
                $user->use($subject);
            });

            /**
            * Assume we have a replacement SubjectUser called NewSubjectUser.
            * We want to verify it behaves identically to SubjectUser, i.e.
            * it uses Subject in the exact same way
            */
            $newSubject = new NewSubjectUser;
            $newSubject->use($mock);
        }

    }

After the ``\Mockery::close()`` call in ``tearDown()`` validates the mock
object, we should have zero exceptions if ``NewSubjectUser`` acted on
`Subject` in a similar way to ``SubjectUser``. By default the order of calls
are not enforced, and loose argument matching is enabled, i.e. arguments may
be equal (``==``) but not necessarily identical (``===``).

If you wished to be more strict, for example ensuring the order of calls and
the final call counts were identical, or ensuring arguments are completely
identical, you can invoke the recorder's strict mode from the closure block,
e.g.

.. code-block:: php

    $mock->shouldExpect(function ($subject) {
        $subject->shouldBeStrict();
        $user = new SubjectUser;
        $user->use($subject);
    });