[Routing] add missing unit tests for Route and RouteCollection classes
minor #9925 [Routing] add missing unit tests for Route and RouteCollection classes (FlorianLB)

This PR was squashed before being merged into the 2.3 branch (closes #9925).

Discussion
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[Routing] add missing unit tests for Route and RouteCollection classes

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | none
| License       | MIT
| Doc PR        | none

Just add few unit tests in Route and RouteCollection classes to have a full coverage.

Commits
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7bbd568 [Routing] add missing unit tests for Route and RouteCollection classes