TestHelper is mostly unnecessary

[freshtonic]

Instead of many permutations of assert_execute_*, let's just have our tests invoke GraphQL.execute, get the response (which may or may not include errors) and check assert on the response directly.

GraphQL.execute is now easier to use because of the use of keyword lists. It means we don't need all of the assert permutations to make it usable anymore.

[aweiker]

I like this and it also makes the tests easier to maintain and read as you don't need to know the correct tuple form.

[freshtonic]

Closed by #86