Testing tools for Tekton Pipelines

I'm not exactly sure what this looks like but I wanted to start tracking this here if ppl have ideas.

Basically I think that we should have a great testing story around Tekton Pipelines, e.g.:

• People should be able to write "unit tests" for their Tasks and Pipelines (I have no idea what these would actually look like!)
• People should be able to have some level of confidence in their Tasks without having to plug them into an entire Pipeline, run them, and observe what happened
• People should be able to express what the intent of their Tasks is, and verify it in some way that isn't manual

For inspiration, I really like the way that OPA polices can have tests written for them: https://www.openpolicyagent.org/docs/latest/how-do-i-test-policies/ Unfortunately Tekton Pipelines is totally different b/c it isn't a language (or is it????) and it's mostly side effect driven (the whole point is to execute stuff that causes changes in the state of the world) but I feel confident that if we really spend some time thinking about this we can make something cool!