Agent skill

test-utility-service

Test utility services that handle external APIs or authorization logic. Use when testing services like AuthenticationService or AuthorizationService. Triggers on "test auth service", "test utility service", "test authentication".

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SKILL.md

Test Utility Service

Tests utility services that call external APIs or provide authorization logic.

Quick Reference

Location: tests/services/{service-name}.service.test.ts Key technique: Mock fetch with vi.stubGlobal

Service Categories

1. External API Services (e.g., AuthenticationService)

Mock network calls and test error handling:

typescript
import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
import { AuthenticationService } from "@/services/authentication.service";
import { env } from "@/env";
import { ServiceUnavailableError, UnauthenticatedError } from "@/errors";

describe("AuthenticationService", () => {
  let service: AuthenticationService;
  const token = "test-token";
  const authServiceUrl = "http://auth-service";

  beforeEach(() => {
    service = new AuthenticationService();
    env.AUTH_SERVICE_URL = authServiceUrl;
  });

  afterEach(() => {
    vi.restoreAllMocks();
  });

  it("authenticates and returns user on success", async () => {
    vi.stubGlobal(
      "fetch",
      vi.fn().mockResolvedValue({
        ok: true,
        json: async () => ({ userId: "user-1", globalRole: "user" }),
      }),
    );

    const result = await service.authenticateUserByToken(token);
    expect(result.userId).toBe("user-1");
  });

  it("throws UnauthenticatedError on 401/403", async () => {
    vi.stubGlobal(
      "fetch",
      vi.fn().mockResolvedValue({
        ok: false,
        status: 401,
      }),
    );

    await expect(service.authenticateUserByToken(token)).rejects.toThrow(
      UnauthenticatedError,
    );
  });

  it("throws ServiceUnavailableError on 5xx", async () => {
    vi.stubGlobal(
      "fetch",
      vi.fn().mockResolvedValue({
        ok: false,
        status: 500,
      }),
    );

    await expect(service.authenticateUserByToken(token)).rejects.toThrow(
      ServiceUnavailableError,
    );
  });

  it("throws ServiceUnavailableError if fetch throws", async () => {
    vi.stubGlobal(
      "fetch",
      vi.fn().mockRejectedValue(new Error("network error")),
    );

    await expect(service.authenticateUserByToken(token)).rejects.toThrow(
      ServiceUnavailableError,
    );
  });

  it("throws ServiceUnavailableError if config missing", async () => {
    env.AUTH_SERVICE_URL = undefined;

    await expect(service.authenticateUserByToken(token)).rejects.toThrow(
      ServiceUnavailableError,
    );
  });

  it("throws UnauthenticatedError if response data invalid", async () => {
    vi.stubGlobal(
      "fetch",
      vi.fn().mockResolvedValue({
        ok: true,
        json: async () => ({ invalid: "data" }),
      }),
    );

    await expect(service.authenticateUserByToken(token)).rejects.toThrow(
      UnauthenticatedError,
    );
  });
});

2. Authorization Services (e.g., AuthorizationService)

Test permission logic with various user/resource combinations:

typescript
import { describe, it, expect, beforeEach } from "vitest";
import { AuthorizationService } from "@/services/authorization.service";
import type { AuthenticatedUserContextType } from "@/schemas/user.schemas";
import type { NoteType } from "@/schemas/note.schema";

const adminUser: AuthenticatedUserContextType = {
  userId: "admin-1",
  globalRole: "admin",
};
const regularUser: AuthenticatedUserContextType = {
  userId: "user-1",
  globalRole: "user",
};
const otherUser: AuthenticatedUserContextType = {
  userId: "user-2",
  globalRole: "user",
};

const noteOwnedByRegularUser: NoteType = {
  id: "note-1",
  content: "Test content",
  createdBy: regularUser.userId,
  createdAt: new Date(),
  updatedAt: new Date(),
};

const noteOwnedByOtherUser: NoteType = {
  id: "note-2",
  content: "Other content",
  createdBy: otherUser.userId,
  createdAt: new Date(),
  updatedAt: new Date(),
};

describe("AuthorizationService", () => {
  let service: AuthorizationService;

  beforeEach(() => {
    service = new AuthorizationService();
  });

  describe("isAdmin", () => {
    it("returns true for admin", () => {
      expect(service.isAdmin(adminUser)).toBe(true);
    });

    it("returns false for regular user", () => {
      expect(service.isAdmin(regularUser)).toBe(false);
    });
  });

  describe("canViewNote", () => {
    it("allows admin", async () => {
      await expect(
        service.canViewNote(adminUser, noteOwnedByRegularUser),
      ).resolves.toBe(true);
    });

    it("allows owner", async () => {
      await expect(
        service.canViewNote(regularUser, noteOwnedByRegularUser),
      ).resolves.toBe(true);
    });

    it("denies non-owner", async () => {
      await expect(
        service.canViewNote(regularUser, noteOwnedByOtherUser),
      ).resolves.toBe(false);
    });
  });

  describe("canCreateNote", () => {
    it("allows admin", async () => {
      await expect(service.canCreateNote(adminUser)).resolves.toBe(true);
    });

    it("allows regular user", async () => {
      await expect(service.canCreateNote(regularUser)).resolves.toBe(true);
    });
  });

  describe("canUpdateNote", () => {
    it("allows admin", async () => {
      await expect(
        service.canUpdateNote(adminUser, noteOwnedByRegularUser),
      ).resolves.toBe(true);
    });

    it("allows owner", async () => {
      await expect(
        service.canUpdateNote(regularUser, noteOwnedByRegularUser),
      ).resolves.toBe(true);
    });

    it("denies non-owner", async () => {
      await expect(
        service.canUpdateNote(regularUser, noteOwnedByOtherUser),
      ).resolves.toBe(false);
    });
  });

  describe("canDeleteNote", () => {
    it("allows admin", async () => {
      await expect(
        service.canDeleteNote(adminUser, noteOwnedByRegularUser),
      ).resolves.toBe(true);
    });

    it("allows owner", async () => {
      await expect(
        service.canDeleteNote(regularUser, noteOwnedByRegularUser),
      ).resolves.toBe(true);
    });

    it("denies non-owner", async () => {
      await expect(
        service.canDeleteNote(regularUser, noteOwnedByOtherUser),
      ).resolves.toBe(false);
    });
  });
});

Key Patterns

Mocking Fetch

typescript
// Success response
vi.stubGlobal(
  "fetch",
  vi.fn().mockResolvedValue({
    ok: true,
    json: async () => ({ data: "value" }),
  }),
);

// Error response
vi.stubGlobal(
  "fetch",
  vi.fn().mockResolvedValue({
    ok: false,
    status: 401,
  }),
);

// Network failure
vi.stubGlobal("fetch", vi.fn().mockRejectedValue(new Error("network error")));

Manipulating Environment

typescript
beforeEach(() => {
  env.AUTH_SERVICE_URL = "http://test-service";
});

it("handles missing config", async () => {
  env.AUTH_SERVICE_URL = undefined;
  // Test behavior
});

Restoring Mocks

typescript
afterEach(() => {
  vi.restoreAllMocks(); // Important!
});

Test Categories for External API Services

Category Test Cases
Success Valid response, correct data returned
Auth Errors (4xx) 401, 403 → UnauthenticatedError
Server Errors (5xx) 500, 502, 503 → ServiceUnavailableError
Network Errors Fetch throws → ServiceUnavailableError
Config Errors Missing URL → ServiceUnavailableError
Validation Errors Invalid response data → appropriate error

Test Categories for Authorization Services

Category Test Cases
Admin Access Admin can do everything
Owner Access Owner can access their own resources
Non-Owner Deny Regular user denied access to others'
Create Access Who can create new resources
Event Access Who can receive real-time events

Complete Examples

See REFERENCE.md for complete test implementations.

What NOT to Do

  • Do NOT forget to restore mocks in afterEach
  • Do NOT test actual network calls (always mock)
  • Do NOT skip testing error scenarios
  • Do NOT skip testing missing configuration
  • Do NOT hardcode URLs (use env variables)

See Also

  • test-service - Guide for choosing test type
  • test-resource-service - Testing resource services
  • create-utility-service - Creating the service to test

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