[Translation] added LoggingTranslator.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #3015, #2435
| License       | MIT
| Doc PR       | symfony/symfony-docs/pull/4050
The container is just a data container, why don't you just test if the data you expect to be added in the container is there rather than writing tests to see if the container gets called the way you think it gets called?

It will make the test easier to update and less fragile, as the inner workings may change over time while the input and output stay the same.