Question

我试图克服一个类具有字符串构造函数参数的情况，该参数不能被Autofixture生成的任何旧字符串（Guid-y外观值）所满足。

在您想要简单地回复Mark Seemann's Ploeh blog entry on Convention-based Customizations的链接之前，请允许我说我已经参考了该测试的其他博客文章，我可以＆＃39 ; t得到通过。

当我在调试中单步执行时，我可以看到构造函数参数在某些时候传入了有效值，但测试仍然失败并带有Guid-y Color值。我认为这与这样一个事实有关，即有一种颜色＆＃39;参数值，和 a＆＃39;颜色＆＃39;由Autofixture填充的属性。是不是我编写了一个解决构造函数参数的ISpecimenBuilder，但是我正在测试公共属性值（两个不同的东西）？

我知道所有这些对于该示例来说都是过度的，但我想到了一个更复杂的场景，其中使用Build<T>().With()方法不会是DRY。

失败测试

    [Fact]
    public void Leaf_Color_Is_Brown()
    {
        // arrange
        var fixture = new Fixture().Customize(new LeafColorCustomization());

        // act
        var leaf = fixture.Create<Leaf>();

        // using .Build<>.With(), test passes
        //var leaf = fixture.Build<Leaf>().With(l => l.Color, "brown").CreateAnonymous();

        // assert
        Assert.True(leaf.Color == "brown");
    }

SUT

    public class Leaf
    {
        public Leaf(string color)
        {
            if (color != "brown")
                throw new ArgumentException(@"NO LEAF FOR YOU!");

            this.Color = color;
        }
        public string Color { get; set; }
    }

CompositeCustomization实现（我知道此示例中不需要AutoMoqCustomization（））

    public class LeafCustomization : CompositeCustomization
    {
        public LeafCustomization()
            : base(
            new LeafColorCustomization(),
            new AutoMoqCustomization()) { }
    }

特定于叶子的ICustomization

    public class LeafColorCustomization : ICustomization
    {
        public void Customize(IFixture fixture)
        {
            if (fixture == null)
                throw new ArgumentNullException("fixture");

            fixture.Customizations.Add(new LeafBuilder());
        }
    }

String-constructor-with-name-of-Color-specific ISpecimenBuilder

    public class LeafBuilder : ISpecimenBuilder
    {
        public object Create(object request, ISpecimenContext context)
        {
            var pi = request as ParameterInfo;
            if (pi == null)
                return new NoSpecimen(request);

            if (pi.ParameterType != typeof(string) || pi.Name != "color")
                return new NoSpecimen(request);

            return "brown";
        }
    }

Answer 1

解决方案1 ：

注册Color可写属性不应作为后处理的一部分分配任何自动值：

internal class LeafColorCustomization : ICustomization
{
    public void Customize(IFixture fixture)
    {
        fixture.Customize<Leaf>(c => c
            .Without(x => x.Color));

        fixture.Customizations.Add(new LeafBuilder());
    }
}

解决方案2 ：

将Color属性设为只读：

public class Leaf
{
    private readonly string color;

    public Leaf(string color)
    {
        if (color != "brown")
            throw new ArgumentException(@"NO LEAF FOR YOU!");

        this.color = color;
    }

    public string Color
    {
        get { return this.color; }
    }
}

由于Color属性是只读的，因此AutoFixture不会为其分配值。

以上解决方案也适用于AutoFixture 2。

Answer 2

假设你单独处理属性设置的东西，这里有一个构造函数参数限制Customization，它可以解决这个问题：

class BrownLeavesCustomization : ICustomization
{
    void ICustomization.Customize( IFixture fixture )
    {
        Func<string> notBrownGenerator = fixture.Create<Generator<string>>()
            .SkipWhile( x => x == "Brown" )
            .First;
        fixture.Customizations.Add( 
            ArgumentGeneratorCustomization<Leaf>.ForConstructorArgument(
                "color", 
                notBrownGenerator ) );
    }

    static class ArgumentGeneratorCustomization<T>
    {
        public static ISpecimenBuilder ForConstructorArgument<TArg>( string argumentName, Func<TArg> generator )
        {
            return new ConstructorArgumentGenerator<TArg>( argumentName, generator );
        }

        class ConstructorArgumentGenerator<TArg> : ISpecimenBuilder
        {
            readonly string _argumentName;
            readonly Func<TArg> _generator;

            public ConstructorArgumentGenerator( string argumentName, Func<TArg> generator )
            {
                Assert.Contains( argumentName, from ctor in typeof( T ).GetConstructors() from param in ctor.GetParameters() select param.Name );
                _argumentName = argumentName;
                _generator = generator;
            }

            object ISpecimenBuilder.Create( object request, ISpecimenContext context )
            {
                var pi = request as ParameterInfo;
                if ( pi == null )
                    return new NoSpecimen( request );
                if ( pi.Member.DeclaringType != typeof( T ) )
                    return new NoSpecimen( request );
                if ( pi.Member.MemberType != MemberTypes.Constructor )
                    return new NoSpecimen( request );
                if ( pi.ParameterType != typeof( TArg ) )
                    return new NoSpecimen( request );
                if ( pi.Name != _argumentName )
                    return new NoSpecimen( request );

                return _generator();
            }
        }
    }
}

Answer 3

解决方案:(基于Mark Seemann的comment on this answer）

在ISpecimenBuilder实现中容纳构造函数参数和可写属性，除了在LeafColorCustomization中添加LeafBuilder实例之外什么都不做：

public class LeafBuilder : ISpecimenBuilder
{
    public object Create(object request, ISpecimenContext context)
    {
        var paramInfo = request as ParameterInfo;
        if (paramInfo != null
            && paramInfo.ParameterType == typeof(string)
            && paramInfo.Name == "color")
        { return "brown"; }

        var propInfo = request as PropertyInfo;
        if (propInfo != null
            && propInfo.PropertyType == typeof(string)
            && propInfo.Name == "Color")
        { return "brown"; }

        return new NoSpecimen(request);
    }
}

internal class LeafColorCustomization : ICustomization
{
    public void Customize(IFixture fixture)
    {
        fixture.Customizations.Add(new LeafBuilder());
    }
}

如何使用Autofixture（v3）与ICustomization，ISpecimenBuilder来处理构造函数参数？

3 个答案: