Cache for generated Test Double code was not updated for Test Stub and Mock Object distinction

[frankdekker]

Q	A
PHPUnit version	10.4.0
PHP version	8.1
Installation Method	Composer

Summary

In PHPUnit 10.4.0 I occassionally get a TestStub class returned instead of a MockObject class as before.

Current behavior

// For any of the return objects another MockObject is created, allowing the following notation to work:
$myClass = $this->createMock(MyClass::class);
$myClass->getTransformer()->getModel()->getData();

How to reproduce

The chaining above fails if in some other test for one of the return objects a TestStub is created. The chained method will then return a TestStub for that class instead of a MockObject, which is not compatible with the method return type and crashes with a type error.

I don't quite understand why, where and how a TestStub is created, but I found the problem where the mix up happens. The problem is because there's a TestStub / MockObject cache, but the generated cache key doesn't differentiate between TestStub and MockObject. See:

Class: PHPUnit\Framework\MockObject\Generator\Generator
Method: generate

Code:

$key = md5(
    $type .
    serialize($methods) .
    serialize($callOriginalClone) .
    serialize($cloneArguments) .
    serialize($callOriginalMethods),
);

My temp fix that seems to work. Add the $mockObject status into the cache key:

$key = md5(
    $type .
    ($mockObject ? 'mock' : 'stub') .
    serialize($methods) .
    serialize($callOriginalClone) .
    serialize($cloneArguments) .
    serialize($callOriginalMethods),
);

[sebastianbergmann]

Thank you for your report.

Please provide a minimal, self-contained, reproducing test case that shows the problem you are reporting.

Without such a minimal, self-contained, reproducing test case I will not be able to investigate this issue.

[frankdekker]

Could you give me a hint when a TestStub is created? If I know that, I can create an example reproduction.

[sebastianbergmann]

createStub($type) is documented to return Stub&$type whereas createMock($type) is documented to return MockObject&$type. Under the hood, however, both createStub($type) and createMock($type) generate and return MockObject&$type for legacy reasons at the moment.

In a future major version of PHPUnit createStub() will be changed to generate and return Stub&$type. This means that expects() will no longer be available on test double objects created using createStub(). For PHPUnit 10.4, the foundation for this change was laid: the test double code generator now uses a flag, $mockObject to control whether a test stub (false) or a mock object (true) should be created. All code paths, except the one used by the return value generator, unconditionally pass true to the test double code generator to maintain backward compatibility.

When a test stub is requested for OriginalType then the name of the generated class is TestStub_OriginalType_random. When a mock object is requested for OriginalType then the name of the generated class is MockObject_OriginalType_random.

However, and like you already noticed, the key for the cache for generated code did not distinguish between test stubs and mock objects.