GraphQL: Refactor the GraphQL Query and Mutation Tests

[gledis69]

The GraphQL query and mutation tests have quite a bit of copy/paste in order to write for all data bases which is good sign that there is room for some refactoring of the test classes.

We can take a:

• GraphQL Pagination tests approach where we hard code the answers so the same code can test all the databases without the need to write specific queries for all the db-s. This might seem like it requires more work due to having to escape many " characters, but this can be done with some smart Find + Replace. This also introduces the overhead of keeping the hard coded data up to date.
• REST tests which share the requests across databases, but each database test class writes its own queries to fetch the right answers from the database.

[Aniruddh25]

purely refactor so moving to M2.

[seantleonard]

let's reevaluate after @aaronpowell merged a PR refactoring the GraphQL test fixture.

[seantleonard]

Our GraphQL tests have adopted some of bullet point 1's proposal since this issue was raised:

• GraphQLFilterTests
• GraphQLMutationTests
• GraphQLPaginationTests
• GraphQLQueryTests
• GraphQLSupportedTypesTests

REST tests also adopt bullet point 2's proposal since this issue was raised:

• Delete
• Find
• Insert
• Patch
• Put

I'm still looking through more of our test project to identify areas where the proposed refactoring could be utilized.