Return Value Generator fails to correctly create test stub for method with static return type declaration when used recursively

[dkarlovi]

Q	A
PHPUnit version	10.4.2
PHP version	8.3.0
Installation Method	Composer

Summary

Given this code

interface CacheItemInterface
{
    public function expiresAfter(int|\DateInterval|null $time): static;
}

interface CacheItemPoolInterface
{
    public function getItem(string $key): CacheItemInterface;
}

running

return $this->getMockBuilder(CacheItemPoolInterface::class)->getMock();

yields

PHPUnit\Framework\MockObject\RuntimeException: Return value for Psr\Cache\CacheItemInterface::expiresAfter() cannot be generated: PHPUnit\Framework\MockObject\ReturnValueGenerator::newInstanceOf(): Return value must be of type PHPUnit\Framework\MockObject\MockObject, TestStub_CacheItemInterface_b24f5332 returned

Changing static to self fixes it.

Current behavior

See above.

How to reproduce

See above.

Expected behavior

Mocking works.

[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.

[dkarlovi]

<?php

require __DIR__ .'/vendor/autoload.php';

interface CacheItemInterface
{
    public function expiresAfter(int|\DateInterval|null $time): static;
}

interface CacheItemPoolInterface
{
    public function getItem(string $key): CacheItemInterface;
}

class MockTestCase extends \PHPUnit\Framework\TestCase
{
    public function testMock(): void
    {
     	$p = $this->getMockBuilder(CacheItemPoolInterface::class)->getMock();
        $i = $p->getItem('aa');
        $i->expiresAfter(1);
    }
}

$ vendor/bin/phpunit TestCase.php 
PHPUnit 10.4.2 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.2.13

E                                                                   1 / 1 (100%)

Time: 00:00.014, Memory: 4.00 MB

There was 1 error:

1) MockTestCase::testMock
PHPUnit\Framework\MockObject\RuntimeException: Return value for CacheItemInterface::expiresAfter() cannot be generated: PHPUnit\Framework\MockObject\ReturnValueGenerator::newInstanceOf(): Return value must be of type PHPUnit\Framework\MockObject\MockObject, TestStub_CacheItemInterface_51dba40f returned

/home/dkarlovi/Development/RandD/phpunit-5593/TestCase.php:21

Same issue with PHP 8.3.0 and PHPUnit 10.5.0

[sebastianbergmann]

Your reproducing test case can be simplified to this:

<?php declare(strict_types=1);
use PHPUnit\Framework\TestCase;

interface AnInterface
{
    public function doSomething(): AnotherInterface;
}

interface AnotherInterface
{
    public function doSomethingElse(): static;
}

final class Issue5593Test extends TestCase
{
    public function testOne(): void
    {
        $a = $this->createStub(AnInterface::class);

        $b = $a->doSomething();

        $b->doSomethingElse();
    }
}

• After $a = $this->createStub(AnInterface::class); you have a test stub of AnInterface in $a
• $a->doSomething() is called and no return value has been configured for AnInterface::doSomething()
• The declared return type for AnInterface::doSomething() is AnotherInterface
• The test double runtime's return value generator generates a test stub for AnotherInterface
• After $b = $a->doSomething(); you have a test stub of AnotherInterface in $b
• $b->doSomethingElse(); is called and no return value has been configured for AnotherInterface::doSomethingElse()
• The declared return type for AnotherInterface::doSomethingElse() is static
• The test double runtime's return value generator generates a test stub for AnotherInterface to satisfy the static return type declaration
• However, this test stub for AnotherInterface causes the test double runtime to error

[dkarlovi]

Why not add the simplified version as a test case?

[sebastianbergmann]

Rest assured, there will be a test case. But that one does not fit and I do not have the time right now to write the test I have in mind.