Velocity Template Engine plugin or extension?

Question

Has anyone tried building Velocity template engine extension or plugin?

Our team is heavily using Velocity Template Language for API input/output transformations. Since a lot of complex logic is in the VTL code, we have implemented a way to unit test the VTL code. However the current problem is that there's no way to measure the code coverage of these unit tests. We want to implement a VTL Engine extension to calculate the coverage when executing these tests. Does anyone have any insight or similar experience?

Thanks!!

Answer 1

Velocity doesn't have this feature yet.

Meanwhile, you can:

• open an issue on Velocity JIRA so that it can get a chance to be included in the next version
• workaround the problem: prepare (automatically!) a copy of your templates where each line is prefixed by a comment with file and line number, and use the tests output to correlate the coverage
• patch Velocity to do so, it's not that hard:
  • the org.apache.velocity.runtime.parser.Node.java class needs a new int field, visited initialized to 0
  • make each render() method increment visited in all the render() method of all other parser nodes which do have such a method
  • after the test case, use a class extending o.a.v.runtime.parser.visitor.BaseVisitor to collect, for each of your template, each node location infos and number of renderings

And if you're successful at this last option, be sure to submit a patch!