.NET 4.0 代码契约 - 它们将如何影响单元测试？

发布于 2024-08-03 18:57:46 字数 862 浏览 6 评论 0原文

例如，这篇文章介绍了它们。

有什么好处？

静态分析看起来很酷，但同时它会阻止在单元测试中将 null 作为参数传递的能力。（如果您遵循本文中的示例）

在单元测试主题上 - 鉴于现在的情况，如果您已经练习了自动化测试，那么代码契约肯定没有意义？

更新

在玩过代码合约后，我有点失望。例如，根据接受的答案中的代码：

public double CalculateTotal(Order order)
{
    Contract.Requires(order != null);
    Contract.Ensures(Contract.Result<double>() >= 0);
    return 2.0;
}

对于单元测试，您仍然必须编写测试以确保不能传递null，并且如果合同中结果大于或等于0是业务逻辑。换句话说，如果我要删除第一个合同，则任何测试都不会中断，除非我专门对此功能进行了测试。然而，这是基于不使用 Visual Studio 更好（终极等）版本中内置的静态分析。

本质上，它们都归结为编写传统 if 语句的另一种方式。我实际使用 TDD 和代码契约的经验说明了原因，以及我是如何做的。

原文

For example this article introduces them.

What is the benefit?

Static analysis seems cool but at the same time it would prevent the ability to pass null as a parameter in unit test. (if you followed the example in the article that is)

While on the topic of unit testing - given how things are now surely there is no point for code contracts if you already practice automated testing?

Update

Having played with Code Contracts I'm a little disappointed. For example, based on the code in the accepted answer:

public double CalculateTotal(Order order)
{
    Contract.Requires(order != null);
    Contract.Ensures(Contract.Result<double>() >= 0);
    return 2.0;
}

For unit testing, you still have to write tests to ensure that null cannot be passed, and the result is greater than or equal to zero if the contracts are business logic. In other words, if I was to remove the first contract, no tests would break, unless I had specifically had a test for this feature. This is based on not using the static analysis built into the better (ultimate etc...) editions of Visual Studio however.

Essentially they all boil down to an alternate way of writing traditional if statements. My experience actually using TDD, with Code Contracts shows why, and how I went about it.

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蓝色星空 2024-08-10 18:57:46

我不认为单元测试和合同相互干扰太多，如果有什么合同应该有助于单元测试，因为它消除了为无效参数添加繁琐的重复测试的需要。契约指定了您可以从函数中期望的最小值，而单元测试则尝试验证特定输入集的实际行为。考虑这个人为的示例：


public class Order
{
    public IEnumerable Items { get; }
}

public class OrderCalculator
{
    public double CalculateTotal(Order order)
    {
        Contract.Requires(order != null);
        Contract.Ensures(Contract.Result<double>() >= 0);

        return 2.0;
    }
}

显然，代码满足合同，但您仍然需要单元测试来验证它的实际行为是否符合您的预期。

I don't think unit testing and contracts interfere with each other that much, and if anything contracts should help unit testing since it removes the need to add tedious repetitive tests for invalid arguments. Contracts specify the minimum you can expect from the function, whereas unit tests attempt to validate the actual behaviour for a particular set of inputs. Consider this contrived example:


public class Order
{
    public IEnumerable Items { get; }
}

public class OrderCalculator
{
    public double CalculateTotal(Order order)
    {
        Contract.Requires(order != null);
        Contract.Ensures(Contract.Result<double>() >= 0);

        return 2.0;
    }
}

Clearly the code satisfies the contract, but you'd still need unit testing to validate it actually behaves as you'd expect.

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