Go: perform type validation in tests

[greg-at-moderne]

What's changed?

What's your motivation?

Anything in particular you'd like reviewers to focus on?

Anyone you would like to review specifically?

Have you considered any alternatives or workarounds?

Any additional context

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've run ./gradlew build locally, and committed any resulting changes to recipes.csv
• I've formatted the lines I changed, without reformatting code I didn't touch

[timtebeek]

As discussed; whilst already valuable, for now this is a misnomer: we only validate no unknowns/erroneous elements are added, whereas we likely want to validate no missing/nil types are present.

TypeValidation itself is misnamed as well, as it's been adding more and more types of validations we could opt into, like the addition that no non-whitespace characters should be present in any prefix, as another guard on the parser we could add here.