Syntactic tests

[justinmchase]

The language should support a syntactic method for writing tests in the same file as the patterns. I'm not totally sure how this should be, will require some research.

Initial thoughts:

• use --- to separate code from tests, multiple --- indicates multiple tests
• test blocks are just object property declarations, where the properties are the shape of a test object
• or maybe its just yaml?
• The test just runs the pattern with the given input, deep equals it to the expected output
• The test object may have some other fields to describe expectations like:
  • throws?: boolean | Pattern
  • matched?: boolean
  • done?: boolean
  • errors?: MachError[]

Letter = "a"-"z"
Main = Letter+
---
input: abc
expected: abc
---
input: abc1
expected: abc
matched: true
done: false