如何单元测试方法调用 IConfiguration.Get<T> 扩展

Question

我有一个非常简单的方法需要进行单元测试。

public static class ValidationExtensions
{
    public static T GetValid<T>(this IConfiguration configuration)
    {
        var obj = configuration.Get<T>();
        Validator.ValidateObject(obj, new ValidationContext(obj), true);
        return obj;
    }
}

问题是configuration.Get<T>是静态扩展方法，不属于IConfiguration。我无法更改该静态方法的实现。

我在想，也许最简单的方法是创建一个内存配置提供程序？但我不知道是否可以在不将其绑定到网络主机的情况下创建一个。

Answer 1

配置模块独立于网络主机相关功能。

您应该能够创建一个内存配置来进行测试，而无需将其绑定到 Web 主机。

查看以下示例测试

public class TestConfig {
    [Required]
    public string SomeKey { get; set; }
    [Required] //<--NOTE THIS
    public string SomeOtherKey { get; set; }
}

//...

[Fact]
public void Should_Fail_Validation_For_Required_Key() {
    //Arrange
    var inMemorySettings = new Dictionary<string, string>
    {
        {"Email:SomeKey", "value1"},
        //{"Email:SomeOtherKey", "value2"}, //Purposely omitted for required failure
        //...populate as needed for the test
    };

    IConfiguration configuration = new ConfigurationBuilder()
        .AddInMemoryCollection(inMemorySettings)
        .Build();

    //Act
    Action act = () => configuration.GetSection("Email").GetValid<TestConfig>();

    //Assert
    ValidationException exception = Assert.Throws<ValidationException>(act);
    //...other assertions of validation results within exception object
}

在我看来，这接近于集成测试，但理想情况下，您只是使用依赖于框架的功能来隔离扩展方法的测试。

Answer 2

解决问题的方式略有不同，避免了 Mock 和大量设置噪音：

InMemoryConfiguration 几乎给了我我需要的东西，所以我扩展了它，以便您可以在构建配置后修改值（我当时的情况我不知道所有模拟值构建配置）

https://gist.github.com/martinsmith1968/9567de76d2bbe537af05d76eb39b1162

底部的单元测试显示用法

Answer 3

大多数模拟库（Moq、FakeItEasy 等）无法模拟扩展方法。

因此，您必须以 IConfiguration.Get<T> 返回 T 实例的方式“填充”您的 IConfiguration。Nkoski 答案适用于 很多 场景，但如果您 需要测试调用IConfiguration.Get<T>的代码，可以使用下面的示例：

using System;
using System.IO;
using System.Text;
using System.Text.Json;
using System.Collections.Generic;
using Microsoft.Extensions.Configuration;
using Xunit;

public class TestClass {
    public class Movie
    {
        public string Name { get; set; }
        public decimal Rating { get; set; }
        public IList<string> Stars { get; set; } //it works with collections
    }

    [Fact]
    public void MyTest()
    {
        var movie = new Movie { 
            Name = "Some Movie",
            Rating = 9, 
            Stars = new List<string>{"Some actress", "Some actor"}
        };

        var movieAsJson = Encoding.UTF8.GetBytes(JsonSerializer.Serialize(movie));
        using(var stream = new MemoryStream(movieAsJson))
        {
            var config = new ConfigurationBuilder().AddJsonStream(stream).Build();
            var movieFromConfig = config.Get<Movie>();
            //var sut = new SomeService(config).SomeMethodThatCallsConfig.Get<Movie>()
        }
    }
}

Answer 4

[TestClass]
public class UnitTest1
{
    [TestMethod]
    public void TestMethod1()
    {
        IConfiguration mock = new MockConfiguration();
        var simpleObject = mock.GetValid<SimpleObject>();
        Assert.AreEqual(simpleObject.MyConfigStr, "123");
    }
}

public class SimpleObject
{
    public string MyConfigStr { get; set; }
}


public class MockConfiguration : IConfiguration
{
    public IConfigurationSection GetSection(string key)
    {
        return new MockConfigurationSection()
        {
            Value = "123"
        };
    }

    public IEnumerable<IConfigurationSection> GetChildren()
    {
        var configurationSections = new List<IConfigurationSection>()
        {
            new MockConfigurationSection()
            {
                Value = "MyConfigStr"
            }
        };
        return configurationSections;
    }

    public Microsoft.Extensions.Primitives.IChangeToken GetReloadToken()
    {
        throw new System.NotImplementedException();
    }

    public string this[string key]
    {
        get => throw new System.NotImplementedException();
        set => throw new System.NotImplementedException();
    }
}

public class MockConfigurationSection : IConfigurationSection
{
    public IConfigurationSection GetSection(string key)
    {
        return this;
    }

    public IEnumerable<IConfigurationSection> GetChildren()
    {
        return new List<IConfigurationSection>();
    }

    public IChangeToken GetReloadToken()
    {
        return new MockChangeToken();
    }

    public string this[string key]
    {
        get => throw new System.NotImplementedException();
        set => throw new System.NotImplementedException();
    }

    public string Key { get; }
    public string Path { get; }
    public string Value { get; set; }
}

public class MockChangeToken : IChangeToken
{
    public IDisposable RegisterChangeCallback(Action<object> callback, object state)
    {
        return new MockDisposable();
    }

    public bool HasChanged { get; }
    public bool ActiveChangeCallbacks { get; }
}

public class MockDisposable : IDisposable
{
    public void Dispose()
    {
    }
}

为 IConfiguration 创建一个模拟并模仿 ConfigBinder 的行为

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Primitives;

为其编译添加了这两个命名空间