unit testing.cs
文件信息
- 📄 原文件：
01_unit_testing.cs - 🔤 语言：csharp
完整代码
csharp
// ============================================================
// 单元测试
// ============================================================
// C# 主流测试框架：xUnit（推荐）、NUnit、MSTest
// xUnit：[Fact] 单个测试，[Theory] 参数化测试
// FluentAssertions：更可读的断言语法
// Moq：Mock 对象，隔离外部依赖
//
// 安装依赖：
// dotnet add package xunit
// dotnet add package xunit.runner.visualstudio
// dotnet add package FluentAssertions
// dotnet add package Moq
// 运行测试：dotnet test
using System;
using System.Collections.Generic;
using System.Linq;
// ============================================================
// 被测试的生产代码
// ============================================================
// ----------------------------------------------------------
// 1. 简单计算器（用于演示基本单元测试）
// ----------------------------------------------------------
class Calculator
{
public int Add(int a, int b) => a + b;
public int Subtract(int a, int b) => a - b;
public int Multiply(int a, int b) => a * b;
public double Divide(double a, double b)
{
if (b == 0)
throw new DivideByZeroException("除数不能为零");
return a / b;
}
public double Power(double base_, double exponent) => Math.Pow(base_, exponent);
}
// ----------------------------------------------------------
// 2. 字符串工具（用于演示边界条件测试）
// ----------------------------------------------------------
class StringUtils
{
public string Reverse(string s)
{
if (s is null) throw new ArgumentNullException(nameof(s));
return new string(s.Reverse().ToArray());
}
public bool IsPalindrome(string s)
{
if (s is null) throw new ArgumentNullException(nameof(s));
s = s.ToLower();
int left = 0, right = s.Length - 1;
while (left < right)
{
if (s[left] != s[right]) return false;
left++;
right--;
}
return true;
}
public string[] SplitWords(string sentence)
{
if (string.IsNullOrWhiteSpace(sentence))
return Array.Empty<string>();
return sentence.Split(' ', StringSplitOptions.RemoveEmptyEntries);
}
}
// ----------------------------------------------------------
// 3. 订单服务（演示依赖注入和 Mock）
// ----------------------------------------------------------
interface IProductRepository
{
decimal GetPrice(string productId);
bool Exists(string productId);
}
interface IOrderLogger
{
void LogOrder(string orderId, decimal total);
}
class OrderService
{
private readonly IProductRepository _repository;
private readonly IOrderLogger _logger;
public OrderService(IProductRepository repository, IOrderLogger logger)
{
_repository = repository;
_logger = logger;
}
public decimal CalculateTotal(Dictionary<string, int> items)
{
decimal total = 0;
foreach (var (productId, quantity) in items)
{
if (!_repository.Exists(productId))
throw new ArgumentException($"商品 {productId} 不存在");
total += _repository.GetPrice(productId) * quantity;
}
return total;
}
public string PlaceOrder(Dictionary<string, int> items)
{
decimal total = CalculateTotal(items);
string orderId = $"ORD-{DateTime.UtcNow:yyyyMMddHHmmss}";
_logger.LogOrder(orderId, total);
return orderId;
}
}
// ============================================================
// 测试代码演示
// ============================================================
// 注意：以下是模拟 xUnit 测试框架的演示写法
// 实际测试需要独立的 Test 项目和 xUnit/NUnit 框架
class TestRunner
{
// 简单的测试结果记录
private static int _passed = 0;
private static int _failed = 0;
private static List<string> _failures = new();
static void Assert(bool condition, string testName)
{
if (condition)
{
_passed++;
Console.WriteLine($" ✓ {testName}");
}
else
{
_failed++;
_failures.Add(testName);
Console.WriteLine($" ✗ {testName}");
}
}
static void AssertEqual<T>(T expected, T actual, string testName)
{
bool condition = EqualityComparer<T>.Default.Equals(expected, actual);
if (condition)
{
_passed++;
Console.WriteLine($" ✓ {testName}");
}
else
{
_failed++;
_failures.Add($"{testName} (期望: {expected}, 实际: {actual})");
Console.WriteLine($" ✗ {testName} (期望: {expected}, 实际: {actual})");
}
}
static void AssertThrows<TException>(Action action, string testName) where TException : Exception
{
try
{
action();
_failed++;
_failures.Add($"{testName} (未抛出 {typeof(TException).Name})");
Console.WriteLine($" ✗ {testName} (未抛出预期异常)");
}
catch (TException)
{
_passed++;
Console.WriteLine($" ✓ {testName}");
}
catch (Exception ex)
{
_failed++;
_failures.Add($"{testName} (抛出了错误类型 {ex.GetType().Name})");
Console.WriteLine($" ✗ {testName} (错误异常类型)");
}
}
static void Main()
{
Console.WriteLine("=== 单元测试演示 ===\n");
// ----------------------------------------------------------
// Calculator 测试
// ----------------------------------------------------------
Console.WriteLine("Calculator 测试:");
var calc = new Calculator();
AssertEqual(8, calc.Add(3, 5), "Add(3,5) = 8");
AssertEqual(0, calc.Add(0, 0), "Add(0,0) = 0");
AssertEqual(-2, calc.Add(-5, 3), "Add(-5,3) = -2");
AssertEqual(5, calc.Subtract(8, 3), "Subtract(8,3) = 5");
AssertEqual(6, calc.Multiply(2, 3), "Multiply(2,3) = 6");
AssertEqual(0, calc.Multiply(0, 100), "Multiply(0,100) = 0");
double divResult = calc.Divide(10, 4);
Assert(Math.Abs(divResult - 2.5) < 1e-10, "Divide(10,4) = 2.5");
AssertThrows<DivideByZeroException>(() => calc.Divide(5, 0), "Divide by zero throws");
// 参数化测试（等价于 [Theory] [InlineData]）
Console.WriteLine("\n 参数化测试 - 加法:");
var addTestCases = new[] { (1, 2, 3), (0, 0, 0), (-1, 1, 0), (100, -50, 50) };
foreach (var (a, b, expected) in addTestCases)
{
AssertEqual(expected, calc.Add(a, b), $"Add({a},{b}) = {expected}");
}
// ----------------------------------------------------------
// StringUtils 测试
// ----------------------------------------------------------
Console.WriteLine("\nStringUtils 测试:");
var utils = new StringUtils();
AssertEqual("olleH", utils.Reverse("Hello"), "Reverse('Hello')");
AssertEqual("", utils.Reverse(""), "Reverse('')");
AssertEqual("a", utils.Reverse("a"), "Reverse('a')");
Assert(utils.IsPalindrome("racecar"), "IsPalindrome('racecar')");
Assert(utils.IsPalindrome("A"), "IsPalindrome('A')");
Assert(!utils.IsPalindrome("hello"), "!IsPalindrome('hello')");
Assert(utils.IsPalindrome(""), "IsPalindrome('')");
AssertThrows<ArgumentNullException>(() => utils.Reverse(null!), "Reverse(null) throws");
// SplitWords
string[] words = utils.SplitWords("Hello World C#");
AssertEqual(3, words.Length, "SplitWords 返回3个词");
AssertEqual("Hello", words[0], "SplitWords[0] = 'Hello'");
string[] empty = utils.SplitWords(" ");
AssertEqual(0, empty.Length, "SplitWords(' ') = 空数组");
// ----------------------------------------------------------
// 测试隔离（Mock 模式）
// ----------------------------------------------------------
Console.WriteLine("\nOrderService 测试（使用测试替身）:");
// 用测试替身替代真实依赖
var mockRepo = new MockProductRepository();
var mockLogger = new MockOrderLogger();
var orderService = new OrderService(mockRepo, mockLogger);
// 场景1：正常下单
var items = new Dictionary<string, int> { { "P001", 2 }, { "P002", 1 } };
decimal total = orderService.CalculateTotal(items);
AssertEqual(299.0m, total, "订单总价 = 299 元");
string orderId = orderService.PlaceOrder(items);
Assert(orderId.StartsWith("ORD-"), "订单ID格式正确");
AssertEqual(1, mockLogger.LoggedOrders.Count, "日志记录了1条订单");
AssertEqual(299.0m, mockLogger.LoggedOrders[0].Total, "日志金额正确");
// 场景2：商品不存在
var badItems = new Dictionary<string, int> { { "INVALID", 1 } };
AssertThrows<ArgumentException>(
() => orderService.CalculateTotal(badItems),
"无效商品抛出 ArgumentException");
// ----------------------------------------------------------
// 测试结果汇总
// ----------------------------------------------------------
Console.WriteLine("\n" + new string('=', 50));
Console.WriteLine($"测试结果: {_passed} 通过 / {_failed} 失败");
if (_failures.Any())
{
Console.WriteLine("失败详情:");
foreach (var f in _failures)
Console.WriteLine($" - {f}");
}
else
{
Console.WriteLine("所有测试通过！");
}
// ----------------------------------------------------------
// xUnit 实际写法示例（注释形式展示）
// ----------------------------------------------------------
Console.WriteLine("\n=== xUnit 实际写法 ===");
Console.WriteLine("""
// 测试类
public class CalculatorTests
{
private readonly Calculator _calc = new();
[Fact]
public void Add_TwoPositiveNumbers_ReturnsSum()
{
var result = _calc.Add(3, 5);
result.Should().Be(8); // FluentAssertions
}
[Theory]
[InlineData(1, 2, 3)]
[InlineData(-1, 1, 0)]
[InlineData(0, 0, 0)]
public void Add_VariousInputs_ReturnsCorrectSum(int a, int b, int expected)
{
_calc.Add(a, b).Should().Be(expected);
}
[Fact]
public void Divide_ByZero_ThrowsDivideByZeroException()
{
Action act = () => _calc.Divide(10, 0);
act.Should().Throw<DivideByZeroException>();
}
}
""");
}
}
// ----------------------------------------------------------
// 测试替身（Test Doubles）
// ----------------------------------------------------------
class MockProductRepository : IProductRepository
{
private readonly Dictionary<string, decimal> _prices = new()
{
{ "P001", 99.50m },
{ "P002", 100.00m },
{ "P003", 49.99m },
};
public decimal GetPrice(string productId) =>
_prices.TryGetValue(productId, out decimal price) ? price : 0;
public bool Exists(string productId) => _prices.ContainsKey(productId);
}
class MockOrderLogger : IOrderLogger
{
public List<(string OrderId, decimal Total)> LoggedOrders { get; } = new();
public void LogOrder(string orderId, decimal total)
{
LoggedOrders.Add((orderId, total));
}
}
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