testing: Use vtk-example as a fallback for prefix

Change-Id: I627bdd7ae131a3eff1b2e08a9b709760af178c28
Fix test function signatures

Change-Id: I851265b552c48e752906f0ff4e109c3a6e6fff9c
testing: Don't look for tests when making an executable

Change-Id: Ib4c263cb6c9dbc97883e1f8276a8a16beb149019
Merge topic 'example-testing-prefix' into master

2c11e597 testing: Don't look for tests when making an executable
7f6395a8 Fix test function signatures
6e1350c0 testing: Use vtk-example as a fallback for prefix