PHPUnit exposes an internal API to the userland

[morozov]

Q	A
PHPUnit version	9.2.3
PHP version	7.4.7
Installation Method	Composer

Summary

In a project that uses PHPUnit and Psalm, Psalm detects the issue in PHPUnit that cannot be fixed in the project and therefore has to be suppressed.

Current behavior

ERROR: InternalMethod - tests/ExampleTest.php:17:12 - The method 
PHPUnit\Framework\MockObject\Builder\InvocationMocker::method has been marked as internal 
(see https://psalm.dev/175)
        )->method('test');

The above is caused by the interface returning a class marked as @internal:

1. phpunit/src/Framework/MockObject/MockObject.php

   Line 24 in 7f664ff

   public function expects(InvocationOrder $invocationRule): BuilderInvocationMocker;

2. phpunit/src/Framework/MockObject/Builder/InvocationMocker.php

   Lines 29 to 32 in cb13599

   	/**
   	* @internal This class is not covered by the backward compatibility promise for PHPUnit
   	*/
   	final class InvocationMocker implements InvocationStubber, MethodNameMatch

This issue was already brought up in #3742 (comment).

How to reproduce

<?php declare(strict_types=1);

namespace Test;

use PHPUnit\Framework\TestCase;

class ExampleTest extends TestCase
{
    /**
     * @test
     */
    public function testExample() : void
    {
        $t = $this->createMock(T::class);
        $t->expects(
            $this->never()
        )->method('test');
    }
}

interface T
{
    public function test() : void;
}

See the full demo project in the gist:

$ composer install
$ vendor/bin/psalm

Since the project's tests extend and use the PHPUnit test classes, suppressing errors in the vendor/ directory doesn't help.

Expected behavior

PHPUnit doesn't expose the internal parts of its API to the userland.

[ostrolucky]

Ref #3236. Looks like we just need to create PR to remove @internal from this class.

[morozov]

@ostrolucky, thanks for the pointer. I thought of adding an interface that extends InvocationStubber and MethodNameMatch. Then, instead of returning an InvocationMocker, the method could return an instance of that interface.

But just removing @internal may be an acceptable short-term solution.