Convert Block test to phpunit

This is not a Unittest as it needs a container right?

  protected function setUp() {
    parent::setUp();

    $this->controller = $this->container->get('plugin.manager.entity')->getStorageController('block');
  }

Thanks to Berdir on irc we got pointer to Change notice
New, separate, extended DrupalUnitTestBase for unit-testing functionality whose dependencies can't be injected
which makes this issue futile.

I partly agree as we can create a mock.

But the tests done in BlockStorageUnitTest are CRUD testing against a plugin which generates stark particular values.

That's way out of my league :(

Added how to test.