added missing unit test
minor #10558 [DependencyInjection] added missing unit test (fabpot)

This PR was merged into the 2.3 branch.

Discussion
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[DependencyInjection] added missing unit test

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Added a unit test to ensure that #10536 won't break BC.

Commits
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47d1592 added missing unit test