Problem

PHPStan includes phpstan/phpstan-phpunit, but it doesn't seem to recognize mocks.

1. phpstan-phpunit 2.0.16 ships with a stub file, MockObject.stub, which contains an empty MockObject interface without an expects() method.
2. When PHPStan analyzes your code, it uses the stub file instead of the real PHPUnit interface.
3. This causes PHPStan to not see the expects() method on mock objects.
   This is a bug in phpstan-phpunit 2.0.16. The stub file, MockObject.stub, must contain a definition of the expects() method.

Reason

Bug in phpstan/phpstan-phpunit version 2.0.16
The stub file /home/mihail/proj/task/vendor/phpstan/phpstan-phpunit/stubs/MockObject.stub contains an empty MockObject interface without an expects() method:
// vendor/phpstan/phpstan-phpunit/stubs/MockObject.stub

namespace PHPUnit\Framework\MockObject;
interface MockObject
{
// EMPTY - no expects() method!
}

However, the real MockObject interface in PHPUnit 11.x has an expects() method:
// vendor/phpunit/phpunit/src/Framework/MockObject/Runtime/Interface/MockObject.php

interface MockObject extends Stub
{
public function expects(InvocationOrder $invocationRule): InvocationMocker;
}

PHPStan uses the stub file instead of the real class, so it doesn't see the expects() method.

Solution

Correct the stub file in phpstan-phpunit. You need to add the expects() method to MockObject.stub.