PHPUnit assert no method is called

Yes, it's quite simple, try this:

$classA->expects($this->never())->method($this->anything());

You can use method MockBuilder::disableAutoReturnValueGeneration.

For example, in your test overwrite default TestCase::getMockBuilder:

    /**
     * @param string $className
     * @return MockBuilder
     */
    public function getMockBuilder($className): MockBuilder
    {
        // this is to make sure, that not-mocked method will not be called
        return parent::getMockBuilder($className)
            ->disableAutoReturnValueGeneration();
    }

Advantages:

• all your mocks won't be expected to call anything than mocked methods. No need to bind ->expects(self::never())->method(self::anything()) to all of them
• you still can set new mocks. After ->expects(self::never())->method(self::anything()) you can't

Works for PhpUnit v7.5.4 (and probably, later ones).