MyDIAPp/__test__/di/WhenManagingDependencies.test.ts

import { describe, it, expect, beforeEach } from 'bun:test';
import { DependencyManager } from '../../src/di/DependencyManager';
import { Logger, Database, UserService } from '../mocks';

describe('When Managing Dependencies', () => {
  let dependencyManager: DependencyManager;

  beforeEach(() => {
    dependencyManager = new DependencyManager();
  });

  describe('GIVEN classes with no dependencies are registered with the dependency manager', () => {
    beforeEach(() => {
      dependencyManager.register('Logger', Logger, [], 'transient');
      dependencyManager.register('Database', Database, [], 'transient');
    });

    it('resolves the class', () => {
      const logger = dependencyManager.resolve<Logger>('Logger');

      expect(logger).toBeDefined();
      expect(logger).toBeInstanceOf(Logger);
    });

    describe('GIVEN the class is registered a second time', () => {
      it('throws an error', () => {
        expect(() => dependencyManager.register('Logger', Logger, [])).toThrow('Error: [Logger] is already registered');
      });
    });
  });

  describe('GIVEN a singleton class is registered with the dependency manager', () => {
    beforeEach(() => {
      dependencyManager.register('Logger', Logger, [], 'singleton');
    });

    it('resolves the class', () => {
      const logger = dependencyManager.resolve<Logger>('Logger');

      expect(logger).toBeDefined();
      expect(logger).toBeInstanceOf(Logger);
    });

    describe('GIVEN a UserService with Logger dependency is registered', () => {
      beforeEach(() => {
        dependencyManager.register('UserService', UserService, ['Logger'], 'singleton');
      });

      it('resolves the same instance when requested multiple times', () => {
        const userService = dependencyManager.resolve<UserService>('UserService');
        const userService2 = dependencyManager.resolve<UserService>('UserService');

        expect(userService).toBe(userService2);
        expect(userService2).toBe(userService);
      });
    });
  });
});