Given you rename the short name of the Test Definition tracker from test_def to something else,
When you display in TTM the dependency graph of a test,
Then the modal title is broken: Dependencies graph of ""

This is due to a hard coded "test_def" in createNodesAndLinksForOutgoingLinks() in plugins/testmanagement/scripts/angular/src/app/artifact-links-graph/artifact-links-model-service.js

In order to fix the issue, one way would be to not rely on the tracker shortname anymore (since everybody can choose its own tracker name, as done in create_test_env plugin). Maybe by relying on the artifact type "_covered_by" ?

However I think that the current representation of the dependencies will better benefit from a less detailed view. As a regular user of TTM, I don't care that there are executions between the test and the campaign. I suggest to display the graph starting on the definition instead of the execution and to bypass the test exec intermediate artifact.

This means that instead of having this:

    campaign 284
    "Tuleap 11.5"         test_def 294
        \              _/ "Set a project as private"
         \           _/
          \         /
           test_exec 340

We will get this:

    campaign 284
    "Tuleap 11.5"
        \
         \
          \
           test_def 294
           "Set a project as private"

Or this:

    campaign 284
    "Tuleap 11.5"          campaign 274
        \                / "Tuleap 11.4"
         \              /
          \            /
           test_def 294
           "Set a project as private"
             /     \_
            /        \_
           /           \_ campaign 254
        campaign 264      "Tuleap 11.2"
        "Tuleap 11.3"

(with probably a switch to toggle on/off closed campaigns to not clutter the view)