How to Write Tests for GraphQL Resolvers in RSpec

#ruby #graphql #test

Before, we wrote resolvers and their corresponding tests in the following manner (with slight modifications to the code):

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

Recent Issue with Resolver

After upgrading graphql-ruby from version 2.3.7 to 2.3.10, I encountered the error undefined method 'types' for nil:NilClass. This change is due to modifications in the library, and upon raising an issue and contacting the author, I was informed that resolvers are not supported outside of GraphQL queries.

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

The author suggested the following alternatives:
1.Using the run_graphql_field Helper:
This method provides a complete GraphQL context.
More details can be found here.
https://graphql-ruby.org/testing/helpers.html

2.Creating a Dummy Query::Context Instance:
Instead of passing context: nil, create a dummy instance.
Though not part of the public API, this workaround should work for now.

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

This Time I Used the First Method, But Here Are Sample Codes 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

I have configured the helper as follows:

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

I have taken the first method of using run_graphql_field this time. Using a dummy Query::Context instance is better as it requires less changes to the existing code base, but I decided it was better to use run_graphql_field for future maintenance as it is not a public API.

🇯🇵 This article is also available in Japanese:
https://zenn.dev/geeknees/articles/842f04ee5d48a3

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How to Write Tests for GraphQL Resolvers in RSpec

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