Use hypothesis-based testing

[ajcr]

There are numerous test cases in this repo, but it is possible that some edge cases have been missed for ordinal comparison and ordinal arithmetic/factorisation.

Using hypothesis could be a way to generate better test-cases and find any missing cases.

• Need to define a strategy for generating transfinite numbers.
• Need to implement some tests as hypothesis based tests. E.g. a**(x + y + z) == a**x * a**y * a**z.