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 must not 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”:

$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.

To create a stub or a mock object with no name, we can call the mock() method with no parameters:

$mock = \Mockery::mock();

As we stated earlier, we don’t recommend creating stub or mock objects without a name.

Classes, abstracts, interfaces

The recommended way to create a stub or a mock object is by using a name of an existing class we want to create a test double of:

$mock = \Mockery::mock('MyClass');

This stub or mock object will have the type of MyClass, through inheritance.

Stub or mock objects can be based on any concrete class, abstract class or even an interface. The primary purpose is to ensure the mock object inherits a specific type for type hinting.

$mock = \Mockery::mock('MyInterface');

This stub or mock object will implement the MyInterface interface.

Note

Classes marked final, or classes that have methods marked final cannot be mocked fully. Mockery supports creating partial mocks for these cases. Partial mocks will be explained later in the documentation.

Mockery also supports creating stub or mock objects based on a single existing class, which must implement one or more interfaces. We can do this by providing a comma-separated list of the class and interfaces as the first argument to the \Mockery::mock() method:

$mock = \Mockery::mock('MyClass, MyInterface, OtherInterface');

This stub or mock object will now be of type MyClass and implement the MyInterface and OtherInterface interfaces.

Note

The class name doesn’t need to be the first member of the list but it’s a friendly convention to use for readability.

We can tell a mock to implement the desired interfaces by passing the list of interfaces as the second argument:

$mock = \Mockery::mock('MyClass', 'MyInterface, OtherInterface');

For all intents and purposes, this is the same as the previous example.

Spies

The third type of test doubles Mockery supports are spies. The main difference between spies and mock objects is that with spies we verify the calls made against our test double after the calls were made. We would use a spy when we don’t necessarily care about all of the calls that are going to be made to an object.

A spy will return null for all method calls it receives. It is not possible to tell a spy what will be the return value of a method call. If we do that, then we would deal with a mock object, and not with a spy.

We create a spy by calling the \Mockery::spy() method:

$spy = \Mockery::spy('MyClass');

Just as with stubs or mocks, we can tell Mockery to base a spy on any concrete or abstract class, or to implement any number of interfaces:

$spy = \Mockery::spy('MyClass, MyInterface, OtherInterface');

This spy will now be of type MyClass and implement the MyInterface and OtherInterface interfaces.

Note

The \Mockery::spy() method call is actually a shorthand for calling \Mockery::mock()->shouldIgnoreMissing(). The shouldIgnoreMissing method is a “behaviour modifier”. We’ll discuss them a bit later.

Mocks vs. Spies

Let’s try and illustrate the difference between mocks and spies with the following example:

$mock = \Mockery::mock('MyClass');
$spy = \Mockery::spy('MyClass');

$mock->shouldReceive('foo')->andReturn(42);

$mockResult = $mock->foo();
$spyResult = $spy->foo();

$spy->shouldHaveReceived()->foo();

var_dump($mockResult); // int(42)
var_dump($spyResult); // null

As we can see from this example, with a mock object we set the call expectations before the call itself, and we get the return result we expect it to return. With a spy object on the other hand, we verify the call has happened after the fact. The return result of a method call against a spy is always null.

We also have a dedicated chapter to Spies only.

Partial Test Doubles

Partial doubles are useful when we want to stub out, set expectations for, or spy on some methods of a class, but run the actual code for other methods.

We differentiate between three types of partial test doubles:

  • runtime partial test doubles,
  • generated partial test doubles, and
  • proxied partial test doubles.

Runtime partial test doubles

What we call a runtime partial, involves creating a test double and then telling it to make itself partial. Any method calls that the double hasn’t been told to allow or expect, will act as they would on a normal instance of the object.

class Foo {
    function foo() { return 123; }
    function bar() { return $this->foo(); }
}

$foo = mock(Foo::class)->makePartial();
$foo->foo(); // int(123);

We can then tell the test double to allow or expect calls as with any other Mockery double.

$foo->shouldReceive('foo')->andReturn(456);
$foo->bar(); // int(456)

See the cookbook entry on Big Parent Class for an example usage of runtime partial test doubles.

Generated partial test doubles

The second type of partial double we can create is what we call a generated partial. With generated partials, we specifically tell Mockery which methods we want to be able to allow or expect calls to. All other methods will run the actual code directly, so stubs and expectations on these methods will not work.

class Foo {
    function foo() { return 123; }
    function bar() { return $this->foo(); }
}

$foo = mock("Foo[foo]");

$foo->foo(); // error, no expectation set

$foo->shouldReceive('foo')->andReturn(456);
$foo->foo(); // int(456)

// setting an expectation for this has no effect
$foo->shouldReceive('bar')->andReturn(999);
$foo->bar(); // int(456)

Note

Even though we support generated partial test doubles, we do not recommend using them.

One of the reasons why is because a generated partial will call the original constructor of the mocked class. This can have unwanted side-effects during testing application code.

See Not Calling the Original Constructor for more details.

Proxied partial test doubles

A proxied partial mock is a partial of last resort. We may encounter a class which is simply not capable of being mocked because it has been marked as final. Similarly, we may find a class with methods marked as final. In such a scenario, we cannot simply extend the class and override methods to mock - we need to get creative.

$mock = \Mockery::mock(new MyClass);

Yes, the new mock is a Proxy. It intercepts calls and reroutes them to the proxied object (which we construct and pass in) for methods which are not subject to any expectations. Indirectly, this allows us to mock methods marked final since the Proxy is not subject to those limitations. The tradeoff should be obvious - a proxied partial will fail any typehint checks for the class being mocked since it cannot extend that class.

Aliasing

Prefixing the valid name of a class (which is NOT currently loaded) with “alias:” will generate an “alias mock”. Alias mocks create a class alias with the given classname to stdClass and are generally used to enable the mocking of public static methods. Expectations set on the new mock object which refer to static methods will be used by all static calls to this class.

$mock = \Mockery::mock('alias:MyClass');

Note

Even though aliasing classes is supported, we do not recommend it.

Overloading

Prefixing the valid name of a class (which is NOT currently loaded) with “overload:” will generate an alias mock (as with “alias:”) except that created new instances of that class will import any expectations set on the origin mock ($mock). The origin mock is never verified since it’s used an expectation store for new instances. For this purpose we use the term “instance mock” to differentiate it from the simpler “alias mock”.

In other words, an instance mock will “intercept” when a new instance of the mocked class is created, then the mock will be used instead. This is useful especially when mocking hard dependencies which will be discussed later.

$mock = \Mockery::mock('overload:MyClass');

Note

Using alias/instance mocks across more than one test will generate a fatal error since we can’t have two classes of the same name. To avoid this, run each test of this kind in a separate PHP process (which is supported out of the box by both PHPUnit and PHPT).

Named Mocks

The namedMock() method will generate a class called by the first argument, so in this example MyClassName. The rest of the arguments are treated in the same way as the mock method:

$mock = \Mockery::namedMock('MyClassName', 'DateTime');

This example would create a class called MyClassName that extends DateTime.

Named mocks are quite an edge case, but they can be useful when code depends on the __CLASS__ magic constant, or when we need two derivatives of an abstract type, that are actually different classes.

See the cookbook entry on Class Constants for an example usage of named mocks.

Note

We can only create a named mock once, any subsequent calls to namedMock, with different arguments are likely to cause exceptions.

Constructor Arguments

Sometimes the mocked class has required constructor arguments. We can pass these to Mockery as an indexed array, as the 2nd argument:

$mock = \Mockery::mock('MyClass', [$constructorArg1, $constructorArg2]);

or if we need the MyClass to implement an interface as well, as the 3rd argument:

$mock = \Mockery::mock('MyClass', 'MyInterface', [$constructorArg1, $constructorArg2]);

Mockery now knows to pass in $constructorArg1 and $constructorArg2 as arguments to the constructor.

Behavior Modifiers

When creating a mock object, we may wish to use some commonly preferred behaviours that are not the default in Mockery.

The use of the shouldIgnoreMissing() behaviour modifier will label this mock object as a Passive Mock:

\Mockery::mock('MyClass')->shouldIgnoreMissing();

In such a mock object, calls to methods which are not covered by expectations will return null instead of the usual error about there being no expectation matching the call.

On PHP >= 7.0.0, methods with missing expectations that have a return type will return either a mock of the object (if return type is a class) or a “falsy” primitive value, e.g. empty string, empty array, zero for ints and floats, false for bools, or empty closures.

On PHP >= 7.1.0, methods with missing expectations and nullable return type will return null.

We can optionally prefer to return an object of type \Mockery\Undefined (i.e. a null object) (which was the 0.7.2 behaviour) by using an additional modifier:

\Mockery::mock('MyClass')->shouldIgnoreMissing()->asUndefined();

The returned object is nothing more than a placeholder so if, by some act of fate, it’s erroneously used somewhere it shouldn’t it will likely not pass a logic check.

We have encountered the makePartial() method before, as it is the method we use to create runtime partial test doubles:

\Mockery::mock('MyClass')->makePartial();

This form of mock object will defer all methods not subject to an expectation to the parent class of the mock, i.e. MyClass. Whereas the previous shouldIgnoreMissing() returned null, this behaviour simply calls the parent’s matching method.