M-T-B-A/backend/tests/unit/services/refund.service.property.test.ts

import * as fc from 'fast-check';

/**
 * **Feature: backend-frontend-integration, Property 6: Refund Rejection Requires Reason**
 * **Validates: Requirements 4.4**
 * 
 * *For any* refund rejection operation, the request SHALL be rejected 
 * if the reason field is empty or contains only whitespace.
 */

/**
 * 模拟退款拒绝验证逻辑
 * 这是一个纯函数，用于属性测试验证业务逻辑的正确性
 */
function validateRejectReason(reason: string | null | undefined): {
  isValid: boolean;
  error?: string;
} {
  // 验证拒绝理由非空
  if (reason === null || reason === undefined) {
    return { isValid: false, error: '拒绝理由不能为空' };
  }
  
  if (typeof reason !== 'string') {
    return { isValid: false, error: '拒绝理由必须是字符串' };
  }
  
  if (reason.trim().length === 0) {
    return { isValid: false, error: '拒绝理由不能为空' };
  }
  
  return { isValid: true };
}

/**
 * 模拟退款拒绝操作
 */
interface MockRefund {
  id: string;
  refundNo: string;
  status: 'Pending' | 'Approved' | 'Rejected' | 'Completed';
  sellerId: string;
}

interface RejectRefundResult {
  success: boolean;
  refund?: MockRefund;
  error?: string;
}

/**
 * 纯函数：模拟退款拒绝逻辑
 */
function simulateRejectRefund(
  refund: MockRefund,
  sellerId: string,
  reason: string | null | undefined
): RejectRefundResult {
  // 1. 验证拒绝理由
  const reasonValidation = validateRejectReason(reason);
  if (!reasonValidation.isValid) {
    return { success: false, error: reasonValidation.error };
  }
  
  // 2. 验证卖家权限
  if (refund.sellerId !== sellerId) {
    return { success: false, error: '无权操作此退款单' };
  }
  
  // 3. 验证退款状态
  if (refund.status !== 'Pending') {
    return { success: false, error: `当前退款状态(${refund.status})不允许拒绝` };
  }
  
  // 4. 执行拒绝操作
  return {
    success: true,
    refund: {
      ...refund,
      status: 'Rejected'
    }
  };
}

describe('RefundService Property Tests', () => {
  describe('Property 6: Refund Rejection Requires Reason', () => {
    it('空字符串作为拒绝理由时应该被拒绝', () => {
      fc.assert(
        fc.property(
          fc.uuid(),
          (sellerId) => {
            const refund: MockRefund = {
              id: 'test-id',
              refundNo: 'RF00000000000000000001',
              status: 'Pending',
              sellerId
            };
            
            const result = simulateRejectRefund(refund, sellerId, '');
            
            // 验证：空字符串应该导致失败
            return result.success === false && result.error === '拒绝理由不能为空';
          }
        ),
        { numRuns: 100 }
      );
    });

    it('仅包含空白字符的理由应该被拒绝', () => {
      fc.assert(
        fc.property(
          fc.uuid(),
          // 生成仅包含空白字符的字符串
          fc.array(fc.constantFrom(' ', '\t', '\n', '\r'), { minLength: 1, maxLength: 20 })
            .map(chars => chars.join('')),
          (sellerId, whitespaceReason) => {
            const refund: MockRefund = {
              id: 'test-id',
              refundNo: 'RF00000000000000000001',
              status: 'Pending',
              sellerId
            };
            
            const result = simulateRejectRefund(refund, sellerId, whitespaceReason);
            
            // 验证：仅空白字符应该导致失败
            return result.success === false && result.error === '拒绝理由不能为空';
          }
        ),
        { numRuns: 100 }
      );
    });

    it('null 或 undefined 作为拒绝理由时应该被拒绝', () => {
      fc.assert(
        fc.property(
          fc.uuid(),
          fc.constantFrom(null as null, undefined as undefined),
          (sellerId, nullishReason) => {
            const refund: MockRefund = {
              id: 'test-id',
              refundNo: 'RF00000000000000000001',
              status: 'Pending',
              sellerId
            };
            
            const result = simulateRejectRefund(refund, sellerId, nullishReason);
            
            // 验证：null/undefined 应该导致失败
            return result.success === false && result.error === '拒绝理由不能为空';
          }
        ),
        { numRuns: 100 }
      );
    });

    it('有效的非空理由应该允许拒绝操作', () => {
      fc.assert(
        fc.property(
          fc.uuid(),
          // 生成非空且不全是空白的字符串
          fc.string({ minLength: 1, maxLength: 200 }).filter(s => s.trim().length > 0),
          (sellerId, validReason) => {
            const refund: MockRefund = {
              id: 'test-id',
              refundNo: 'RF00000000000000000001',
              status: 'Pending',
              sellerId
            };
            
            const result = simulateRejectRefund(refund, sellerId, validReason);
            
            // 验证：有效理由应该成功
            return result.success === true && result.refund?.status === 'Rejected';
          }
        ),
        { numRuns: 100 }
      );
    });

    it('理由前后的空白应该被忽略，但中间内容有效则应该成功', () => {
      fc.assert(
        fc.property(
          fc.uuid(),
          // 生成带有前后空白的有效理由
          fc.tuple(
            fc.array(fc.constantFrom(' ', '\t'), { minLength: 0, maxLength: 5 }).map(a => a.join('')),
            fc.string({ minLength: 1, maxLength: 50 }).filter(s => s.trim().length > 0),
            fc.array(fc.constantFrom(' ', '\t'), { minLength: 0, maxLength: 5 }).map(a => a.join(''))
          ).map(([prefix, content, suffix]) => prefix + content + suffix),
          (sellerId, reasonWithWhitespace) => {
            const refund: MockRefund = {
              id: 'test-id',
              refundNo: 'RF00000000000000000001',
              status: 'Pending',
              sellerId
            };
            
            const result = simulateRejectRefund(refund, sellerId, reasonWithWhitespace);
            
            // 验证：有实际内容的理由应该成功
            return result.success === true;
          }
        ),
        { numRuns: 100 }
      );
    });

    it('非 Pending 状态的退款单不能被拒绝', () => {
      fc.assert(
        fc.property(
          fc.uuid(),
          fc.constantFrom('Approved' as const, 'Rejected' as const, 'Completed' as const),
          fc.string({ minLength: 1, maxLength: 50 }).filter(s => s.trim().length > 0),
          (sellerId, nonPendingStatus, validReason) => {
            const refund: MockRefund = {
              id: 'test-id',
              refundNo: 'RF00000000000000000001',
              status: nonPendingStatus,
              sellerId
            };
            
            const result = simulateRejectRefund(refund, sellerId, validReason);
            
            // 验证：非 Pending 状态应该失败
            return result.success === false && 
                   result.error?.includes('不允许拒绝');
          }
        ),
        { numRuns: 100 }
      );
    });

    it('非本店铺的退款单不能被拒绝', () => {
      fc.assert(
        fc.property(
          fc.uuid(),
          fc.uuid(),
          fc.string({ minLength: 1, maxLength: 50 }).filter(s => s.trim().length > 0),
          (refundSellerId, querySellerId, validReason) => {
            // 确保两个卖家ID不同
            if (refundSellerId === querySellerId) return true;
            
            const refund: MockRefund = {
              id: 'test-id',
              refundNo: 'RF00000000000000000001',
              status: 'Pending',
              sellerId: refundSellerId
            };
            
            const result = simulateRejectRefund(refund, querySellerId, validReason);
            
            // 验证：非本店铺应该失败
            return result.success === false && 
                   result.error === '无权操作此退款单';
          }
        ),
        { numRuns: 100 }
      );
    });
  });
});