removed @covers annotations
minor #1571 removed @covers annotations (fabpot)

This PR was merged into the 1.16-dev branch.

Discussion
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removed @covers annotations

I propose to remove the `@covers` annotations for the following main reasons:

 * they were only used in a limited number of test cases;
 * they limited the code coverage of nodes for no reasons (some other tests are as valid to test the nodes).

Commits
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4ba0789 removed @covers annotations