diff --git a/src/__tests__/lib/order/fee.test.ts b/src/__tests__/lib/order/fee.test.ts
new file mode 100644
index 0000000..3fe0101
--- /dev/null
+++ b/src/__tests__/lib/order/fee.test.ts
@@ -0,0 +1,69 @@
+import { describe, it, expect } from 'vitest';
+import { calculatePayAmount } from '@/lib/order/fee';
+
+describe('calculatePayAmount', () => {
+  it.each([
+    { rechargeAmount: 100, feeRate: 0, expected: '100.00', desc: 'feeRate=0 返回原金额' },
+    { rechargeAmount: 100, feeRate: -1, expected: '100.00', desc: 'feeRate<0 返回原金额' },
+    { rechargeAmount: 100, feeRate: 3, expected: '103.00', desc: '100 * 3% = 3.00' },
+    { rechargeAmount: 100, feeRate: 2.5, expected: '102.50', desc: '100 * 2.5% = 2.50' },
+    { rechargeAmount: 99.99, feeRate: 1, expected: '100.99', desc: '99.99 * 1% = 0.9999 → ROUND_UP → 1.00, total 100.99' },
+    { rechargeAmount: 10, feeRate: 3, expected: '10.30', desc: '10 * 3% = 0.30' },
+    { rechargeAmount: 1, feeRate: 1, expected: '1.01', desc: '1 * 1% = 0.01' },
+  ])('$desc (amount=$rechargeAmount, rate=$feeRate)', ({ rechargeAmount, feeRate, expected }) => {
+    expect(calculatePayAmount(rechargeAmount, feeRate)).toBe(expected);
+  });
+
+  describe('ROUND_UP 向上取整', () => {
+    it('小数第三位非零时进位', () => {
+      // 33 * 1% = 0.33, 整除无进位
+      expect(calculatePayAmount(33, 1)).toBe('33.33');
+    });
+
+    it('产生无限小数时向上进位', () => {
+      // 10 * 3.3% = 0.33, 精确
+      expect(calculatePayAmount(10, 3.3)).toBe('10.33');
+      // 7 * 3% = 0.21, 精确
+      expect(calculatePayAmount(7, 3)).toBe('7.21');
+      // 1 * 0.7% = 0.007 → ROUND_UP → 0.01
+      expect(calculatePayAmount(1, 0.7)).toBe('1.01');
+    });
+  });
+
+  describe('极小金额', () => {
+    it('0.01 元 + 1% 手续费', () => {
+      // 0.01 * 1% = 0.0001 → ROUND_UP → 0.01
+      expect(calculatePayAmount(0.01, 1)).toBe('0.02');
+    });
+
+    it('0.01 元 + 0 手续费', () => {
+      expect(calculatePayAmount(0.01, 0)).toBe('0.01');
+    });
+  });
+
+  describe('大金额', () => {
+    it('10000 元 + 2.5%', () => {
+      // 10000 * 2.5% = 250.00
+      expect(calculatePayAmount(10000, 2.5)).toBe('10250.00');
+    });
+
+    it('99999.99 元 + 5%', () => {
+      // 99999.99 * 5% = 4999.9995 → ROUND_UP → 5000.00
+      // 但 rechargeAmount 传入为 number 99999.99，Decimal(99999.99) 可能有浮点
+      // 实际: 99999.99 + 5000.00 = 104999.99
+      expect(calculatePayAmount(99999.99, 5)).toBe('104999.99');
+    });
+  });
+
+  describe('精度', () => {
+    it('输出始终为 2 位小数', () => {
+      const result = calculatePayAmount(100, 0);
+      expect(result).toMatch(/^\d+\.\d{2}$/);
+    });
+
+    it('有手续费时输出也为 2 位小数', () => {
+      const result = calculatePayAmount(77, 3.33);
+      expect(result).toMatch(/^\d+\.\d{2}$/);
+    });
+  });
+});
diff --git a/src/__tests__/lib/order/limits.test.ts b/src/__tests__/lib/order/limits.test.ts
new file mode 100644
index 0000000..7bcea84
--- /dev/null
+++ b/src/__tests__/lib/order/limits.test.ts
@@ -0,0 +1,141 @@
+import { vi, describe, it, expect, beforeEach } from 'vitest';
+
+vi.mock('@/lib/db', () => ({
+  prisma: {
+    order: { groupBy: vi.fn() },
+  },
+}));
+
+vi.mock('@/lib/config', () => ({
+  getEnv: vi.fn(),
+}));
+
+vi.mock('@/lib/payment', () => ({
+  initPaymentProviders: vi.fn(),
+  paymentRegistry: {
+    getDefaultLimit: vi.fn(),
+  },
+}));
+
+import { getEnv } from '@/lib/config';
+import { paymentRegistry } from '@/lib/payment';
+import { getMethodDailyLimit, getMethodSingleLimit } from '@/lib/order/limits';
+
+const mockedGetEnv = vi.mocked(getEnv);
+const mockedGetDefaultLimit = vi.mocked(paymentRegistry.getDefaultLimit);
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  // 默认：getEnv 返回无渠道限额字段，provider 无默认值
+  mockedGetEnv.mockReturnValue({} as ReturnType<typeof getEnv>);
+  mockedGetDefaultLimit.mockReturnValue(undefined as any);
+});
+
+describe('getMethodDailyLimit', () => {
+  it('无环境变量且无 provider 默认值时返回 0', () => {
+    expect(getMethodDailyLimit('alipay')).toBe(0);
+  });
+
+  it('从 getEnv 读取渠道每日限额', () => {
+    mockedGetEnv.mockReturnValue({
+      MAX_DAILY_AMOUNT_ALIPAY: 5000,
+    } as any);
+    expect(getMethodDailyLimit('alipay')).toBe(5000);
+  });
+
+  it('环境变量 0 表示不限制', () => {
+    mockedGetEnv.mockReturnValue({
+      MAX_DAILY_AMOUNT_WXPAY: 0,
+    } as any);
+    expect(getMethodDailyLimit('wxpay')).toBe(0);
+  });
+
+  it('getEnv 未设置时回退到 provider 默认值', () => {
+    mockedGetEnv.mockReturnValue({} as any);
+    mockedGetDefaultLimit.mockReturnValue({ dailyMax: 3000 } as any);
+    expect(getMethodDailyLimit('stripe')).toBe(3000);
+  });
+
+  it('getEnv 设置时覆盖 provider 默认值', () => {
+    mockedGetEnv.mockReturnValue({
+      MAX_DAILY_AMOUNT_STRIPE: 8000,
+    } as any);
+    mockedGetDefaultLimit.mockReturnValue({ dailyMax: 3000 } as any);
+    expect(getMethodDailyLimit('stripe')).toBe(8000);
+  });
+
+  it('paymentType 大小写不敏感（key 构造用 toUpperCase）', () => {
+    mockedGetEnv.mockReturnValue({
+      MAX_DAILY_AMOUNT_ALIPAY: 2000,
+    } as any);
+    expect(getMethodDailyLimit('alipay')).toBe(2000);
+  });
+
+  it('未知支付类型返回 0', () => {
+    expect(getMethodDailyLimit('unknown_type')).toBe(0);
+  });
+
+  it('getEnv 无值且 provider 默认值也无 dailyMax 时回退 process.env', () => {
+    mockedGetEnv.mockReturnValue({} as any);
+    mockedGetDefaultLimit.mockReturnValue({} as any); // no dailyMax
+    process.env['MAX_DAILY_AMOUNT_ALIPAY'] = '7777';
+    try {
+      expect(getMethodDailyLimit('alipay')).toBe(7777);
+    } finally {
+      delete process.env['MAX_DAILY_AMOUNT_ALIPAY'];
+    }
+  });
+});
+
+describe('getMethodSingleLimit', () => {
+  it('无环境变量且无 provider 默认值时返回 0', () => {
+    expect(getMethodSingleLimit('alipay')).toBe(0);
+  });
+
+  it('从 process.env 读取单笔限额', () => {
+    process.env['MAX_SINGLE_AMOUNT_WXPAY'] = '500';
+    try {
+      expect(getMethodSingleLimit('wxpay')).toBe(500);
+    } finally {
+      delete process.env['MAX_SINGLE_AMOUNT_WXPAY'];
+    }
+  });
+
+  it('process.env 设置 0 表示使用全局限额', () => {
+    process.env['MAX_SINGLE_AMOUNT_STRIPE'] = '0';
+    try {
+      expect(getMethodSingleLimit('stripe')).toBe(0);
+    } finally {
+      delete process.env['MAX_SINGLE_AMOUNT_STRIPE'];
+    }
+  });
+
+  it('process.env 未设置时回退到 provider 默认值', () => {
+    mockedGetDefaultLimit.mockReturnValue({ singleMax: 200 } as any);
+    expect(getMethodSingleLimit('alipay')).toBe(200);
+  });
+
+  it('process.env 设置时覆盖 provider 默认值', () => {
+    process.env['MAX_SINGLE_AMOUNT_ALIPAY'] = '999';
+    mockedGetDefaultLimit.mockReturnValue({ singleMax: 200 } as any);
+    try {
+      expect(getMethodSingleLimit('alipay')).toBe(999);
+    } finally {
+      delete process.env['MAX_SINGLE_AMOUNT_ALIPAY'];
+    }
+  });
+
+  it('无效 process.env 值回退到 provider 默认值', () => {
+    process.env['MAX_SINGLE_AMOUNT_ALIPAY'] = 'abc';
+    mockedGetDefaultLimit.mockReturnValue({ singleMax: 150 } as any);
+    try {
+      expect(getMethodSingleLimit('alipay')).toBe(150);
+    } finally {
+      delete process.env['MAX_SINGLE_AMOUNT_ALIPAY'];
+    }
+  });
+
+  it('未知支付类型返回 0', () => {
+    expect(getMethodSingleLimit('unknown_type')).toBe(0);
+  });
+});