Add ability to easily test/verify edge expressions

**Is your feature request related to a problem? Please describe.**
Small typos in an `expr` can be easy to miss.

We should have a way to test & verify these edge expressions.

**Describe the solution you'd like**
1. Have a way to expose/print edge transitions to verify what was interpolated. E.g. app.edge_logic() -> List[conditions]..
2. Have "edge transition" logic log decisions being made. E.g. this condition evaluated to false, this condition evaluated to True, ... or using default edge.
3. Have a way to test them -- not sure what the best way is here. But it's basically a test of the graph in a way...

**Describe alternatives you've considered**
N/A

**Additional context**