- Use better error messages with more context.
- Unify their validation logic and share tests.
- Validate also type of the name.
- Refactor node (Script/Category) parser tests for easier future
changes and cleaner test code (using `TestBuilder` to do dirty work in
unified way).
- Add more tests. Custom `Error` properties are compared manually due to
`chai` not supporting deep equality checks (chaijs/chai#1065,
chaijs/chai#1405).
