Symfony version(s) affected: 4.2.1

Description
While using PHPUnit 7.5 mocks the DebugClassLoader reports

The "PHPUnit\Framework\MockObject\MockObject" interface extends "PHPUnit_Framework_MockObject_MockObject" that is deprecated Use PHPUnit\Framework\MockObject\MockObject instead.

As you can see, the first interface and one suggested are exactly the same that correctly extends the deprecated interface in order to not break BC.

How to reproduce
Just use a simple $this->createMock in PHPUnit 7.5 test case.