Testing GraphQL APIs in GraphQL

// Unit testing resolvers
const { expect } = require('chai');
const sinon = require('sinon');

describe('User Resolvers', () => {
  let db;
  
  beforeEach(() => {
    // Mock database
    db = {
      user: {
        findUnique: sinon.stub(),
        findMany: sinon.stub(),
        create: sinon.stub(),
        update: sinon.stub()
      }
    };
  });
  
  describe('Query.user', () => {
    it('should return user by id', async () => {
      const mockUser = { id: '1', name: 'John' };
      db.user.findUnique.resolves(mockUser);
      
      const result = await resolvers.Query.user(
        null,
        { id: '1' },
        { db }
      );
      
      expect(result).to.deep.equal(mockUser);
      expect(db.user.findUnique.calledWith({
        where: { id: '1' }
      })).to.be.true;
    });
    
    it('should throw error if user not found', async () => {
      db.user.findUnique.resolves(null);
      
      try {
        await resolvers.Query.user(null, { id: '999' }, { db });
        expect.fail('Should have thrown');
      } catch (error) {
        expect(error.message).to.include('not found');
      }
    });
  });
});

// Integration testing with test server
const { ApolloServer } = require('@apollo/server');
const { gql } = require('graphql-tag');

describe('GraphQL Integration Tests', () => {
  let server;
  
  beforeEach(() => {
    server = new ApolloServer({ typeDefs, resolvers });
  });
  
  it('should fetch users', async () => {
    const GET_USERS = gql`
      query {
        users {
          id
          name
          email
        }
      }
    `;
    
    const res = await server.executeOperation(
      { query: GET_USERS },
      { contextValue: { db: mockDb, user: { id: '1', role: 'USER' } } }
    );

    // Results live under res.body.singleResult
    expect(res.body.singleResult.errors).to.be.undefined;
    expect(res.body.singleResult.data.users).to.be.an('array');
  });
  
  it('should create post', async () => {
    const CREATE_POST = gql`
      mutation CreatePost($title: String!, $content: String!) {
        createPost(title: $title, content: $content) {
          id
          title
          content
        }
      }
    `;
    
    const res = await server.executeOperation(
      {
        query: CREATE_POST,
        variables: {
          title: 'Test Post',
          content: 'Test content'
        }
      },
      { contextValue: { db: mockDb, user: { id: '1', role: 'USER' } } }
    );

    expect(res.body.singleResult.errors).to.be.undefined;
    expect(res.body.singleResult.data.createPost).to.include({
      title: 'Test Post',
      content: 'Test content'
    });
  });
});