.. index::
single: Reference; Creating Test Doubles
Creating Test Doubles
=====================
Mockery's main goal is to help us create test doubles. It can create stubs,
mocks, and spies.
Stubs and mocks are created the same. The difference between the two is that a
stub only returns a preset result when called, while a mock needs to have
expectations set on the method calls it expects to receive.
Spies are a type of test doubles that keep track of the calls they received, and
allow us to inspect these calls after the fact.
When creating a test double object, we can pass in an identifier as a name for
our test double. If we pass it no identifier, the test double name will be
unknown. Furthermore, the identifier does not have to be a class name. It is a
good practice, and our recommendation, to always name the test doubles with the
same name as the underlying class we are creating test doubles for.
If the identifier we use for our test double is a name of an existing class,
the test double will inherit the type of the class (via inheritance), i.e. the
mock object will pass type hints or ``instanceof`` evaluations for the existing
class. This is useful when a test double must be of a specific type, to satisfy
the expectations our code has.
Stubs and mocks
---------------
Stubs and mocks are created by calling the ``\Mockery::mock()`` method. The
following example shows how to create a stub, or a mock, object named "foo":
.. code-block:: php
$mock = \Mockery::mock('foo');
The mock object created like this is the loosest form of mocks possible, and is
an instance of ``\Mockery\MockInterface``.
.. note::
All test doubles created with Mockery are an instance of
``\Mockery\MockInterface``, regardless are they a stub, mock or a spy.