support_backend/tests/concurrency/assignment-race.test.ts

import { describe, it, expect, beforeAll, afterAll } from 'vitest';
import { buildApp } from '@/app';
import { prismaClient } from '@/infrastructure/database';
import { FastifyInstance } from 'fastify';
import { loginAs, authHeader } from '../helpers/auth';
import {
  encryptCredential,
  generateCredentialSecret,
  issueIntegrationToken,
} from '@/modules/catalog/products';
import { assignmentEngine } from '@/modules/orchestration/assignments';

/**
 * specs/016-load-concurrency-testing User Story 1 / FR-001 / SC-001: two or more concurrent
 * assignment attempts on the same ticket must never leave more than one Assignment row marked
 * `isCurrent`. Before research.md §1's fix (a Postgres partial unique index on
 * `assignments(ticketId) WHERE isCurrent = true`, plus a bounded retry in
 * AssignmentRepository.createAssignment), Postgres's default READ COMMITTED isolation let two
 * concurrent `assignmentEngine.assignToSpecificNode` calls each see "nothing current to
 * supersede" and both successfully create their own `isCurrent: true` row.
 */
describe('Assignment double-assignment race (User Story 1)', () => {
  let app: FastifyInstance;
  let authToken: string;
  const externalProductId = `TEST_ASSIGN_RACE_PROD_${Date.now()}`;
  const skillTag = `assign_race_skill_${Date.now()}`;
  let productId: string;
  let teamId: string;
  const agentIds: string[] = [];
  let nodeId: string;
  let secret: string;
  const createdTicketIds: string[] = [];

  async function createTicket(): Promise<string> {
    const token = issueIntegrationToken(secret, {
      externalProductId,
      tenantId: 'tenant-1',
      userId: 'user-1',
    });
    const created = await app.inject({
      method: 'POST',
      url: '/v1/support/requests',
      headers: { authorization: `Bearer ${token}` },
      payload: {
        productId: externalProductId,
        tenantId: 'tenant-1',
        userId: 'user-1',
        source: 'test',
        problem: `Assignment race test ${Date.now()}-${Math.random()}`,
      },
    });
    expect(created.statusCode).toBe(202);
    const ticketId = created.json().data.ticketId as string;
    createdTicketIds.push(ticketId);
    return ticketId;
  }

  beforeAll(async () => {
    app = await buildApp();
    authToken = await loginAs(app, 'ADMIN');

    const product = await prismaClient.product.create({
      data: { externalProductId, name: 'Assignment Race Test Product', status: 'active' },
    });
    productId = product.id;
    secret = generateCredentialSecret();
    await prismaClient.productIntegration.create({
      data: {
        productId,
        credentialRef: encryptCredential(secret),
        authMechanism: 'signed_token',
        allowedScope: { tenantIds: ['tenant-1'] },
        status: 'active',
        rateLimitPerMinute: 1000,
        rateLimitPerUserPerMinute: 1000,
      },
    });

    const team = await app.inject({
      method: 'POST',
      url: '/admin/teams',
      headers: authHeader(authToken),
      payload: { name: `Assign Race Team ${Date.now()}` },
    });
    teamId = team.json().data.id;

    // Several eligible agents so a race has real agents to (incorrectly) double-assign across,
    // not just one candidate every attempt would trivially agree on.
    for (let i = 0; i < 5; i++) {
      const agent = await app.inject({
        method: 'POST',
        url: `/admin/teams/${teamId}/agents`,
        headers: authHeader(authToken),
        payload: { name: `Assign Race Agent ${i}` },
      });
      const agentId = agent.json().data.id;
      agentIds.push(agentId);
      await app.inject({
        method: 'PUT',
        url: `/admin/agents/${agentId}/skills/${skillTag}`,
        headers: authHeader(authToken),
        payload: { level: 3 },
      });
    }

    const node = await app.inject({
      method: 'POST',
      url: '/admin/hierarchy-nodes',
      headers: authHeader(authToken),
      payload: {
        name: 'Assign Race Node',
        order: 0,
        productScope: [externalProductId],
        skills: [skillTag],
        assignmentStrategy: 'ROUND_ROBIN',
      },
    });
    nodeId = node.json().data.id;
  });

  afterAll(async () => {
    const ticketFilter = { ticketId: { in: createdTicketIds } };
    await prismaClient.assignmentHistory.deleteMany({ where: ticketFilter });
    await prismaClient.assignment.deleteMany({ where: ticketFilter });
    await prismaClient.hierarchyNode.deleteMany({ where: { id: nodeId } });
    await prismaClient.agentSkill.deleteMany({ where: { agentId: { in: agentIds } } });
    await prismaClient.agent.deleteMany({ where: { teamId } });
    await prismaClient.team.deleteMany({ where: { id: teamId } });
    await prismaClient.ticketMessage.deleteMany({ where: ticketFilter });
    await prismaClient.ticket.deleteMany({ where: { id: { in: createdTicketIds } } });
    await prismaClient.problem.deleteMany({ where: { productId } });
    await prismaClient.productIntegration.deleteMany({ where: { productId } });
    await prismaClient.product.deleteMany({ where: { id: productId } });
    await app.close();
  });

  it('leaves exactly one current assignment after 20 genuinely concurrent assignment attempts', async () => {
    const ticketId = await createTicket();

    const attempts = 20;
    await Promise.all(
      Array.from({ length: attempts }, () =>
        assignmentEngine.assignToSpecificNode(ticketId, nodeId, 'system', 'concurrency test'),
      ),
    );

    const currentAssignments = await prismaClient.assignment.findMany({
      where: { ticketId, isCurrent: true },
    });
    expect(currentAssignments.length).toBe(1);

    // Every attempt was still recorded (superseded or current) — the race must not have
    // silently dropped attempts, only converged them onto a single current row.
    const allAssignments = await prismaClient.assignment.findMany({ where: { ticketId } });
    expect(allAssignments.length).toBe(attempts);
  });

  it(
    'holds consistently across 10 repeated runs (SC-001: zero exceptions)',
    async () => {
      for (let run = 0; run < 10; run++) {
        const ticketId = await createTicket();

        await Promise.all(
          Array.from({ length: 20 }, () =>
            assignmentEngine.assignToSpecificNode(ticketId, nodeId, 'system', `run ${run}`),
          ),
        );

        const currentAssignments = await prismaClient.assignment.findMany({
          where: { ticketId, isCurrent: true },
        });
        expect(currentAssignments.length).toBe(1);
      }
    },
    60000,
  );
});