How to Test GraphQL Resolvers with RSpec

Previously, I was writing (or rather, there was) the following Resolvers and their corresponding tests.
The code has been slightly modified.

module Resolvers
  class Users < Resolvers::Base
    type ObjectTypes::User.connection_type, null: false

    description 'Find users by roles. You can pass XXX_role or [XXX_role, YYY_role].'

    argument :role, [EnumTypes::User::Role]

    def resolve(role:)
      if role&.include?('evaluation_role')
        User.evaluation_users
      elsif role&.include?('level_aptitude_role')
        User.level_aptitude_users
      else
        User.where(role: role)
      end
    end
  end
end

require 'rails_helper'

RSpec.describe Resolvers::Users do
  describe '#resolve' do
    context 'when role includes evaluation_role' do
      it 'returns evaluation test users filtered by service' do
        user1 = create(:user, role: 'evaluation_role')
        user2 = create(:user, role: 'evaluation_role')
        allow(User).to receive(:evaluation_test_users).and_return([user1, user2])

        result = described_class.new(object: nil, field: nil, context: nil).resolve(role: ['evaluation_role'])

        expect(result).to contain_exactly(user1, user2)
      end
    end
  end
end

When I upgraded the graphql-ruby version from 2.3.7 to 2.3.10, I began encountering an undefined method types' for nil:NilClass` error.

This change was caused by the modification linked below. I opened an issue to inquire with the author, who informed me that Resolvers are not supported outside of GraphQL queries.

https://github.com/rmosolgo/graphql-ruby/commit/db7a9bcaceb77dc0af78b73e0d5c2ad849c27598#diff-fdbf285d34242cb3cb7b1e56e80f5d39bc600246e72b7bb32190e555432f156cR39

The author suggested the following two alternatives:

• Use the run_graphql_field helper, which provides a complete GraphQL context.
  • https://graphql-ruby.org/testing/helpers.html
• Alternatively, create a dummy Query::Context instance and pass it instead of context: nil.
  • Although this is outside the scope of GraphQL-Ruby's public API, they mentioned it should work for the time being.

query_ctx = GraphQL::Query.new(MySchema, "{ __typename }").context

In this instance, we opted for the former approach, but I will provide sample code for both.

require 'rails_helper'

RSpec.describe Resolvers::Users, type: :graphql do
  describe '#resolve' do
    subject { run_graphql_field("Query.users", nil, arguments: { role: role }).items }

    let!(:user1) { create(:user, role: 'evaluation_role') }
    let!(:user2) { create(:user, role: 'evaluation_role') }

    context 'when role includes evaluation_role' do
      let(:role) { 'evaluation_role' }

      it {
        expect(subject).to eq [user2, user2]
      }
    end
  end
end

require 'rails_helper'

RSpec.describe Resolvers::Users do
  describe '#resolve' do
    subject { resolver.resolve(role: role) }

    let(:query_ctx) { GraphQL::Query.new(TofflerSchema, "{ __typename }").context }
    let(:resolver) { described_class.new(object: nil, context: query_ctx, field: nil) }
    let!(:user1) { create(:user, role: 'evaluation_role') }
    let!(:user2) { create(:user, role: 'evaluation_role') }

    context 'when role includes evaluation_role' do
      let(:role) { 'evaluation_role' }

      it {
        expect(subject).to eq [user2, user1]
      }
    end
  end
end

Additionally, the helper is configured as follows:

 config.with_options type: :graphql do |graphql_config|
    graphql_config.include GraphQL::Testing::Helpers.for(MySchema)
  end

The issue containing this discussion can be found here:
ref. https://github.com/rmosolgo/graphql-ruby/issues/5040

In this case, we chose the first method, which uses run_graphql_field. While the approach using a dummy Query::Context instance requires fewer changes to the existing codebase, we decided that run_graphql_field would be better for future maintenance since the other method is not part of the public API.