Tests a GraphQL Yoga server (the-guild.dev runtime) with `yoga.fetch()` for in-process, no-network request simulation of queries and mutations, `@graphql-tools/executor-http` for subscription and incremental-delivery (streaming) tests, auth-header pass-through, and production-config gates for disabled introspection and persisted operations. Use to test a GraphQL Yoga server, write Yoga query, mutation, or subscription tests, or check its production plugin config; for a different runtime harness use apollo-server-tests, mercurius-tests, or hasura-tests instead, not this skill.